Precision: 38 Digits After The Point

How "Mobile TeleSystems" rates services and produces bills for subscribers.
The Soviet reality has taught us to live from salary to salary and has made us to believe that if sellers used to cheat with weights and sell expired  products, so everyone at vegetable markets everyone seemed to be an enemy. Now we are still surrounded by these problems, moreover they are multiplying. For example, one of the gossip themes is how mobile operators are cheating on their clients.
To clarify the issue, we have addressed Mr. S. Stroganov, the head of MTS settlements department.

Question: Many MTS subscribers are interested, how the company implements a billing system. How "appropriate" is it? Does anybody check the system?
Answer: MTS implements a certified billing system from a Russian provider. I would like to emphasize this fact, since Russian systems comply maximally with peculiarities of our legislation and the national accounting system, as well as subscriber specifics. Foreign developers usually do not take these peculiarities into account, that is why reports, generated by these systems, do not provide all information, necessary for clients and supervision bodies.
In the framework of monitoring of licensed activity, company operations are supervised by GosSvyazNadzor. The billing system is under monitoring too. Moreover, MTS is constantly under auditing control, which compares rating methods with tariffs declared by our company. Auditors conduct their own tests and check benchmarks, performed in the framework of our internal control. Currently, audit of information systems responsible for subscriber servicing is completed. Functionalities of payment collection, financial control and accounting reports have been checked. The conclusion, provided by auditors, has confirmed efficiency of our operations.
But, of course, our main auditors are subscribers, who can check correctness of charges for services provided by ordering an itemized bill at any time. At MTS, the level of bill itemization is high, we can specify every call made. In a monthly bill we reflect all services charged. But if a subscriber is still not sure, it is possible to address the financial control department and obtain all necessary documents with explanations from our specialists.
Question: Although your billing system is extremely reliable, is there a chance for an error?
Answer: The share of errors is insignificantly miniscule. Moreover, rounding is sometimes taken for an error. Our system stores information with precision up to 38 digits after the point. We show two digits to subscribers, sometimes four digits after the point, and, when a subscriber adds several intermediate values from the bill, the total can be one or two cents different from the bill total, since we operated with more precise values, than specified in the bill.
Question: How working with subscribers is organized?
Answer: We have two methods of settlements with subscribers - credit and advance. The credit scheme is used, mainly, to service large organizations, having a good credit history. We use the advance method to work with private subscribers. The advance system is good, since a subscriber has an account, which is a wallet. Money from this wallet may be spent not only on telecom services, but also, for instance, on provision of Internet access via dedicated lines. These services may also include real mobile commerce.
But in any case, we provide strict control over subscriber expenses and a wide spectrum of services. MTS is trying to make payment simple and convenient for subscribers. We have introduced scratch cards, we are cooperating with several banks that ensure fast registration of payments to subscriber accounts at MTS. Today subscribers in Moscow can pay for services using a credit card at MTS offices, in banks or even by phone.
Question: How call duration is turned into money?
Answer: You make a call, then hang up, and the switch registers a call. There has not been any interaction between the switch and billing system yet. This interaction is governed by a special schedule, according to which the information on the call made at the certain moment is received by the billing system. The schedule depends on the load on the switch and the billing system, time of the day, and is modified even if you are changing geographical position during the call. When the information is received by the billing system, it is rated according to tariffs, thus influencing subscriber's account balance.
Question: And how does the billing system operate in roaming?
Answer: If a subscriber is in roaming, the frequency of receiving files with information on the calls depends on the operator, in which zone the subscriber is and may vary from several hours to one and a half days. But roaming agreements allow delays of sending such information up to 30 days (it is acceptable by international practice). Calculation of your account balance, thus,  may be delayed. The most complicated case is when a subscriber visited in coverage zones of several operators simultaneously and the handset was switching from one network to another depending on coverage conditions. In this case calls, rated by one operator may influence the subscriber balance earlier, than calls, made by the same subscriber in another operator's network during the same period of time.
Question: But funds are often debited from subscriber accounts with delay even after conventional calls. Why?
Answer: In the advance method, there is no online information flow about the calls registered by the database. Information on services provided is received and rated intermittently. It may be accounted for by the following parameters: subscriber current location (coverage zone of home or guest billing system, national or international roaming), as well as load on the switch and the billing systems, which depends on subscriber overall activity, during daytime or in the evening. Periodic services have their own specifics: firstly, the subscription fee. In the credit method, the fee for periodic services is debited once a month. In the advance method, on the other hand, charge posting is flexible. Usually, we charge a periodic services fee once every two or three days.
Question: Why it is impossible to debit accounts regularly?
Answer: Irregularity of debiting, among other things, is connected to system performance. To ensure better customer care, we do our best to purchase modern, high-performance equipment. However, there are restrictions on such import to Russia, imposed by the US Congress. The licensing procedure is bureaucratic and consumes much time. For instance, we have to prove every time that we are not going to engage in nuclear research and provide our data center resources to other companies, etc. Although, still according to unconfirmed information, the procedure of licensing server import is going to be simplified.
Anyway, we understand that irregular debiting is not convenient for subscribers and are trying to find a decent solution to this problem. Currently works for launching new server equipment are in progress. We hope this will allow to make gaps in charging subscription fee smaller.
Question: How are one-time services rated?
Answer: Currently we are considering a possibility of instant rating for one-time services, i.e. at the moment they are provided. It is already implemented for several services, but there are specific services, which cannot be rated immediately. It is caused rather by the fact that the system should operate seamlessly and perform a lot of various operations simultaneously, than by specifics of these services. For instance, at the moment of bill creation - which is the billing process - a client uses a one-time service. In this case, we have to use the subscriber account simultaneously for service rating and for billing, which is impossible. We have either to postpone billing and calculate the account balance later, or postpone rating of this particular service until the account is free, which is currently done. But MTS is already working to ensure instant rating of all services.
Question: Sometimes subscribers are suspended even with a positive account balance. How can you explain this?
Answer: We have the financial control system, which uses subscriber loyalty. Loyalty is viewed as timely payments and a number of forced suspensions. The greater the number of forced suspensions, the lower is the reliability category. Such notions as "full" or "partial" suspensions are related to reliability categories. Subscribers are fully suspended when account balance reaches the null value, partial suspension in several reliability categories prohibits outgoing calls though the balance is positive. We specify in the customer care contract that MTS reserves the right to limit provision of some services when the account balance reaches a certain threshold.
Question: When does subscriber suspension occur?
Answer: The threshold for partial suspension is 10 dollars. For all "cheap" tariffs the reliability category is high, and there is no partial suspension, but, if the subscriber fails to pay regularly, the reliability category is automatically lowered and partial suspension becomes possible. The rule is simple - you should try to pay before your phone is suspended. When the subscriber starts to make advance payments regularly, the reliability category increases. I would like to say, that our system is configured to be the most friendly towards subscribers. At first, we activate phones of suspended subscribers who made advance payments, and then suspend debtors, and finally, add new services.
Question: Suppose, the terminal has been unexpectedly suspended. What can be done in such a situation?
Answer: First of all, you should check your balance by calling the Automatic Call Center. You may also call the MTS Directory (0890). It is possible even in full suspension mode. If lack of funds is the reason for suspension, you should make a payment.
Question: And how can subscribers control their balance immediately?
Answer: It is relatively simple. First, you may dial 088011 and MTS Automatic Call Center tells the approximate balance (round-up to dollars). Currently we are servicing more than one thousand of such calls per minute in peak hours. Second, by adding ICS service you will be able to track your expenditures via Internet. Probably, we will use the following technology: the balance menu item will appear in the handset. After you select this item you receive a short message with your balance. If a subscriber has any questions about the balance, our Financial Control department (0876) should be called. This is how a lot of disputable questions were solved in several minutes.
Question: What can be done, if account balance is low and you are out of town or abroad?
Answer: The best situation is when a subscriber has a scratch card. In this case it is necessary to dial 7670880 - the Moscow number of the Automatic Call Center, or 7660166 - the information service of the Customer Care department. But we also support other payment methods. A subscriber may sign a contract for automatic withdrawal of funds from a credit card and then to specify the amount to be transferred from the credit card to MTS account during a phone call to the Automatic Call Center.
Disclosed information, particularly phone numbers and available payment methods, is provided for subscribers of the MTS Moscow zone and may differ for other regions.