MTN gave me a phone without IMEI Number!!!!!

On Friday 24 July 2015 I took in my cell phone in for repairs at the MTN Store Cnr Rivonia & Summit Road, in Morningside. The phone ran out of battery the day before and it did not want to charge. I received an SMS on Monday 27 July 2015 to say that the phone has been taken to the repairs center. And since then I did not get any sort of communication regarding the progress of the repairs. Today 03 August 2015 I receive another SMS saying that my phone was ready for collection. I went to the store and when I get there I am told that nothing was done on my phone because the repair center says that my phone was tempered with. I then asked the consultant what they meant because the phone has never been at any other repair center besides them. The consultant was not really interested in assisting me and he said that I should call the HVRCRepair call center. I have a serious issue with MTN, Firstly this phone has never been at any repair center besides this one, can someone please explain to me what makes them say that the phone has been tempered with. So this means that MTN gave a phone on my contract which has no IMEI number!!!!