For Vodacom users in South Africa experiencing the SMS sending problem:

Your current PDU number is 059128721992 but that is too short. The actual full number is 0591287219921100 but it doesn't get recognised so the fix is to change the '05' to '07' and add the 1100 to the end so your new SMSC number is 0791287219921100

Steps:

1) Dial *#*#4636#*#*
2) Select Phone Information
3) Set SMSC number to 0791287219921100 and hit Update
4) Turn radio off and back on
5) enjoy sending an sms