The Internet often cut off! (MTS, USB modem, GPRS connection) What could be wrong?

Question

Computer networks

Provider - MTS
time - approximately from December 20
1 First, the laptop stops seeing the device (modem)
2 The connection disappears and the network signal bars
3 naturally, it does not connect again on its own.

Answer 1

1) Test the modem on another computer.
2) Check the operation of another modem on this computer.
3) Check the operation of the Internet by phone with the same provider.
But the magic ball suggests that the modem most likely died.