Extremely bad customer service from MTN

My phone has been with MTN for over two months for repairs of a cracked screen. Three weeks ago I was told that it repaired and ready to be dispatched to me on condition that I pay the required access fee. I paid it and sent the proof to the insurance department as requested. A few days later I got an email from the repair centre asking me to pay and send them the proof. I forwarded the original email with proof attached that had been sent to mtn insurance. When I enquired about when I would get my phone, I was simply told \we have to wait for mtn insurance to give us the go ahead first\". This is totally unacceptable especially because mtn insurance does not even answer calls when you call them on ***. I'might paying for a a monthly contract but MTN is not giving me my phone back. What should I do now???"