To enable MMS and Tethering, you might have to install a carrier-specific file for your carrier.
If you look at the
.ipcc-file you'll notice that it's a standard ZIP archive. Inside you'll find a folder
and a folder with your carrier's name. There you'll find a file
carrier.list along some others. It is an XML file
with all the features for your carrier. Some interesting snippets:
<key>AllowEDGEEditing</key> <true/> <key>AllowMMSCEditing</key> <true/> <key>AllowMMSEditing</key> <true/>
<false/> <key>ShowCallForwarding</key> <false/> <key>ShowTTY</key> <!-- Show options for TTY devices --> <false/>