I need to cancel my contract

This is a formal compliant concerning my relationship with telkom, ever since I have been usisng their network. They have managed to make my life a living hell since I opened up a contract with them. I was given a faulty phone. The phone which is an Experia E1 has had problems since the 3rd month I had it, till this day. I reported my phone the first time at maponya mall and it came back fixed, not two months passed and the phone stopped working again. The second time I took to rosebank mall at a telkom store for repairs and it came back working. Its less than a month now and the phone yet again has stopped working. I am furious with telkom and I do not want their further services. I WANT NOTHING TO DO WITH THIS PHONE OR CONTRACT. I pay every month for this phone, but I don't get to use it because it never works.