As I wrote in past, one of targets in next stable Gammu release is to have much better support for Motorola phones. The biggest problem with them is that Motorola separated AT commands in two separate subsets and each can be issued in different phone mode. I just hacked support for this into Gammu, so basic operations with Motorola phones should work.
If you have Motorola phone, I'll welcome you to test new code. Just download current snapshot or use subversion to get latest code, compile it and run against your phone.