Terrible Service from Telkom

I started a new cellphone contract with Telkom online with the specific requirement that i will keep my existing number. They promised that it was no problem but changed the number without further discussion with me and now refuse to give me any feedback on the issue. I visited the branch in Mossel Bay four times now and was promised that this problem will recieve urgent attention two weeks ago without any resolve. I want to cancel the contract as Telkom did not keep their promise to retain my number.