Cancel my new MTN contract because of no service

I am very unhappy with Mtn Direct. They are fast and eager to give you a new contract but if you have a problem there is absolutly no assistance!! When I took the new contract I clearly stated that I would need to port a Vodacom pay as you go number. Now the Mtn shop states I can't do a port. Unless I can't port the contract is useless!! I send an email with no response. I tried phoning them but it rings with no answer!! How can I cancel this contract??? The service is up to sh*t and if it starts like this....