Mysterious Dial Tones - Automatically

    If typing ATH0 (or AT then anything) gives you a dial tone, then
there has been a string sent to the modem without a carraige return.
So the original ATxxxxx is waiting for a carraige return and when
you type the next A(Txxx) the modem gets ATA which tells it to pick
up the line.  You'll have to check your software and find the string
with NO carriage return, and put it in.