PAYING FOR A NON WORKING CELLPHONE

on the 16th January this year i took my phone to telkom clearwater because it was not charging. They promised me that it will be back within 21 working days, after 21 days i called them to ask about the phone but it wasn't fixed. I called them again a week later and they told me it was there. When i got there the phone was still not fixed and the manager(MARY) said she will look into the matter and she will call me on monday(she never called). I then called on Monday to make a follow-up and i was told that the phone is gone for repairs. After a week i called and they said it was still there at repair and as soon as it arrived they will give me a call. More than 2 months after i booked my phone i went there again today(27th March 2015) to check what was wrong since no one is calling me(they have never called me for a feedback all this time my phone was with them), when i got there i was shocked to find out that my phone is still in their stockroom and has never been sent for repair. i cancelled my contract but now they are threatening me with charges for cancelling the contract. Why should i pay for something which I'm not using.....I need help> THANKS