Does Nokia 7600 (or other UMTS Nokia mobile phones) support AT commands and/or TAPI standard, in particular the commands set for sending/receiving SMS/MMS/voice calls over 3G networks directly via PC link through HyperTerminal?
WCDMA phones support basically the same AT command set as GSM phones. There are no MMS AT commands supported.
There *are* AT command differences between phones, (some support more that others), and I can't say for certain about the 7600, but yes, more than likely SMS commands are supported, as well as basic voice call commands.
Check ncsp.forum.nokia.com/content under "Messaging" to find AT command set documents.