Bad servise always

Mtn has done it again, Bought Blackberry Z3 fro Truworths in Clearwater, it worked for less than 3 months, Had a network problem, called their call centre who asked me to take out sim and restart phone, I did but that did not work, booked it for repair, Now told that I have to pay R2100 because the sim pin is broken or pay R330 for them to return back my phone unfixed. I bought the phone for R2400, meaning sim pin is R2100 more expensive than phone .I have been sending them emails, they only respond with automated email promising to get back to me. This phone is a compact phone, never opened and they themselves agreed.