Repair of Phone under Warranty

Vodacom for my thinking has got too big and have no interest in servicing their clients, I work for a corporate client who has many hundresds if not thousands of Cell Phone contracts with Vodacom. My 8 month old Sony xperia stopped working 7 weeks ago at which point i sent the phone back to Vodacom for repair, Under Vodacoms agreement we have an SLA that states the phone under warranty would be repaired by Vodacom within 7 days and if they cannot repair the phone it would be sent to the supplier for repair and could take 14 days. Two weeks after sending the phone in for repairs i queried the repair and was informed that it could not be repaired as they could not verify the IMEI number which had been given to them as the phone was a sealed unit. After much backwards and forwards with proof of Invoices and delivery notes being supp**** Vodacom said they would get the phone repaired by Sony. This process took more than 5 weeks to resolve a week later Vodacom informed me that they had goods news the phone would be repaired at no cost to me,like they were doing me a favor what a load of hogwash the phone is under warranty so there should be no charge. 7 weeks later i'm still waiting