Here's a list of commands, as best as I can remember without digging out the docs (which are at home).
Any character sent to the modem while it is dialing or negotiating will result in the connection being dropped and the modem going on-hook. Commands can be terminated by a CR, or LF, but not both.
I'm doing this from memory. I have the complete specs at home (somewhere) from when I worked at Hayes. If you need more details, feel free to contact me at the e-mail address below.