"pppd" under Linux vs Korean phone

I have a mobile phone which after being connected to computer
though the USB is seen from the kernel as an ACM device.
It works with "minicom" as ordinary serial port but after
the message connect appears on the screen it refuses to do anything.
The worse "pppd" pointed being launch to handle that device
gives debug messages that it attempts to send some requests
and gets no replay. After the "pppd" outs when timeout is reached.

The phone itself gives nothing on the terminal,
after the message "CONNECT" appears on the screen.
But when I put to the appropriate port of the phone
prerecorded message from PPP protocol conversation
it returned 32 bytes of the same conversation but only ones.

Well, could somebody advice how to get it working.

-Michael the friend of D