I think I still have the US Robotics 56k kicking around somewhere but I ditched the hardline eons ago!
AT Commands, GSM AT command set:
https://www.engineersgarage.com/tutorials/at-commands-gsm-at-command-set/
AT Commands For Wireless GSM/GPRS Modems with IP Connectivity (PDF file):
I used for search criteria:
“at commands over wireless connection”
I've got one in my mitts.
Used to run a BBS. Friend put his (PCBoard software) in an obscure IP location, network accessible. Was a hoot to use, takes one back to some faded memories. Gone now. He retired from ISPing.