I suspect what you're seeing is related to the way the call is set up on a GSM modem. From memory the dialling portion happens much like an ISDN, so the pauses and extra digits are all presented at the same time as the dialled number.
So there may be a command to make it behave more like a V.32/V.34 modem, as opposed to one signalling by V.110 or V.120
As a start I'd try AT+CBST=7,0,1;+CHSN=1,1,0,4 as my init string and see if that makes a difference - that ought to make your phone emulate a V.32 9600 baud modem - more than adequate for terminal work.