For example, users of the tariff under the name "Maxi Plus" can obtain information about the balance on the account by using toll-free numbers *100*1#. And at the rate of "Ultra", apart from other advantages (such as unlimited SMS and MMS messages, no roaming charges, unlimited Internet), there is also room personal customer service 0990, where you can learn about the number remaining on the account minutes.
MTS provides a number of packages (50, 100 and 300). To activate any of them (let's say 300 units), you need to dial USSD-command *707*13#. To find out about your unspent traffic, the subscriber needs to use a query to *706#.
We should not forget about such a convenient service as the "Internet Assistant". Just go to the website operator, select your region and then click on a tab. There you will be able not only to learn about the remaining minutes, but to manage the connected services to activate new or deactivate the old.