Will the subscriber switch to the new tariff? State the monthly subscription fee for the tariff the subscriber will choose for 2020.

The problem does not provide enough information to determine if the subscriber will switch to the new tariff. To make this decision, we would need to know the subscriber's actual usage of calls, internet, and SMS in 2019 to compare it with the cost of the new tariff. Therefore, we cannot determine the monthly subscription fee for the tariff the subscriber will choose for 2020.