Under garentee query - long outstanding repairs

Have submitted an iPhone 7 under guarantee for repairs to MTN Ballito Junction Store where it was purchased from. This phone was submitted under its year guarantee, it was told to me that it will be submitted under its guarantee conditions. Now 2 months 10 days down the line I still have not yet received my phone back from repairs. MTN repairs now claims that my phone is out of its guarantee repairs condition which now results in a R4000-00 repair cost. I have not yet received any communication via emails or sms from their repair facility but it was reveal to me today after numerous calls and visits to the MTN Store. iPhone 7- IMEI Number: ***