2nd Possible Solution:
Try changing the Alltel MMSC setting's to match what's below:
-Server Name: Leave that the same
-Gateway: Delete this, leaving it blank
-Port number: 8080
-Server address:
http://mms-mt.alltel.net/servlets/mms
-Connect via: Alltel Wireless (your isp, or internet)
-WAP: WAP 2.0