I am a little concerned here as there could be more than one problem.
The first question is, are you able to detect dialtone from this gsm device when you use the test command? If so, then the basic is ready.
The second question/concern is you say that this is a GSM modem. Does this mean that you will be doing data/modem calls and not voice calls? If this is the case, then I have never seen pure data/modem calls work through an A800 before, and I have seen a lot A800’s.
If you are doing just voice, then do not set any of the modem stuff as the GSM device is not a really a modem.
Please clarify this and feel free to contact me at my email of firstname.lastname@example.org