Unfair account billings

Late November i was bought a ring at Sterns Tygervalley, it was then too small. So we sent it back to a Stern Prominade mall for exchange 3 days later. They said they wont be able to exchange it as it had stones missing so they can only send it for re sizing. We agreed for it to be sent being aware that it will cost us an extra charge but we will get a qoute before it is fix. We were never called for the amount of the quotation and when it was back we did not recieve any communication. When we phoned we were told the amount of money that is due. The amount for re sizing is more than the amount the ring was bought for. We cant seem to get any explanation on how is that possible. TFG please see to this because we are not going to pay this ridiculous amount just to resize a ring. Job no is JC ********** 007855.