paying for something that was not fixed!

my blackberry torch needed to be repaired. Since it was purchased from Foschini Chatsworth and does have an insurance on it, I took it to them. They advised it will need to be sent to the MTN repair center and if they cant repair it, it will be sent to the insurance and I would need to pay an excess on first claim of R250. Which was fine. I thereafter get told mtn cannot repair it and I need to cough up an amount of R330 for a service charge for something they could not fix and was not told to me! they now refuse to waiver the cost and its useless trying to call them as the phones just ring. I don't see how I need to pay them for a service charge for not fixing the phone and to pay excess on top of that. Foschini has tried to get them to waiver the cost and mtn is just not interested. I can only imagine how many customers this is happening too who doesn't understand that this should not be a charge. I work for an insurance company and I want to know what exactly im paying that service charge for since nothing was done and if mtn is aware of CPA and FAIS and they have no rights to hold my phone for this payment. it does not belong to them!