Telkom refuse to cancel my contract

I took out a contract with Telkom for 24 months ago. Now I am up for an upgrade, I dont want an upgrade I want that contract canceled, I went on the help line they say I must contact through email. When they call me they say they cannot cancel for me. Why when taking a contract it's easy, when I dont need it it's difficult to cancel. I dont think I will use telkom again. I even have a second contract for data.