Thanks, Jeff, for your comprehensive answers. As per #2 it was my fault (ATFX_PHDRPY was called instead of ATFX_RESLN).
Another small question, how to properly organize fax session if I want to send/receive a color fax when the other end can accept it and b/w fax if it can't? As far as I understand from docs I should use only RAW files for sending and receiving, analyze coding by ATFX_CODING after phase B and according to this info use the proper fax file (colored or b/w) , am I right?