Not responding to AT commands, gsm modem?

Question

Command line

What an hour I've been trying to get an answer to at least the usual "AT" command, and two times it still gave out OK, the "SMSCaster E-Marketer" program normally sends SMS and so on. But nothing special from putty. terminal programs are not issued. I can't imagine what it could be. Modem: MULTIBAND 900E 1800. Already wrote a program in C #, again, "OK" was issued only after the modem was rebooted (disconnected from the network). I thought that the problem was in the modem itself, but this idea was refuted by the same program that successfully sends SMS. I really don't know how to solve this problem, does anyone know?