Hello all,
I have been doing something similar with an Ericsson T68I phone.
I communicated at 1200 buad and use AT command set.
I am NOT trying to send SMS, but DTMF tones. I am getting the phone to dial by using the access keypad AT command (rather than ATD command, which for some reason wouldn't work) and then activating send DTMF tones. Sorry I can't remember what the AT for these are, but what I dis was successful withoput too much trouble. Simple serout at N1200 (without MAX232 chip) was the most successful from a 4MHz 'F84. The T68I is autobaud so will talk at most baud rates above 1200.