You are probably talking at cross-purposes: you require, specifically, Circuit-Switched Data (CSD); they are probably using “data” generically, and thinking of IP-based data.
See above - they are probably not using “data call” in any technical sense!
No, they are (almost certainly) not random - that will be raw PPP frames that you’re seeing: FAQ forum/wiki? - #9 by awneil
They are probably doing their best - but just not understanding the question.
They are trained & equipped to deal with average-joe consumers using (smart)phones - not M2M developers.
This is the problem with using a consumer SIM!
You should try talking to your local Distributor - they may have experience with how to get what you want from AT&T.
Your best option would be to go to a proper M2M service provider who will actually know & understand what you’re talking about…