Waiting for refund

My phone was send in to the repair centre for a new screen, after 6 weeks the mtn store in Klerksdorp let me know I must paid over the money for the screen R1730 and I did. After that they let me know they cant fix the phone, I received the phone back but up to date I am still waiting for my refund, every week they need something else. The money was paid over 13/3/15 and still no refund. Very bad service and I took my phone to a repair centre in Klerksdorp and they fix it immediately. I want my refund please.