I want to cancel my contract!!!

Had my contract for 9 months and still waiting for my Gb per month. Always an excuse and they are rectifying the problem. Ive asked to cancel my contract as this is a bridge of contract. I signed up for this contract with 1gb per month and i have not received it ever. I am still waiting for contact details on who to contact to cancel my contract. This is pathetic. But MTN is quick to suspend my line if payment does not reflect in their account on time even if payment was made on time! Im gatvol! No one ever calls me back!