What does it mean to be reminded of the expiration of telecom credit?

Will give users a certain amount of overdraft consumption to avoid being shut down.

Telecom credit expiration reminder means that when the user owes money, the telecom company gives the user a certain overdraft consumption limit to avoid being shut down. Credit is the maximum amount of telephone charges that users can overdraw. When the user's overdraft consumption reaches the credit limit, it will be stopped, and the user needs to pay all overdraft fees according to the regulations.