MTN cannot tell me where my phone is

Good day. On 10/3/2015 I gave my son's damaged phone in for repair at the MTN shop in the Vaal Mall. They gave me the documentation with an IMEI number - ***. On 19/3/2015 I tried to call the repair centre, but they don't answer the phone. I sent an email to [Email Removed] and they informed me that there is no such a record. On 22/3/2015 I called the MTN shop in Vaal Mall and Stefan van den Berg said he will call me on Monday. I received a call from Stefan on Monday, informing me that there is no such IMEi number. I asked him where my son's phone was and he couldn't answer me. I send him the documentation and demanded feedback. I tried to call the regional office *** and *** without any answer. I WANT MY SON'S PHONE BACK!!!!!! I just wonder, what did they do with the phone? (I have this \lost"phone on contract at MTN) I need someone to give me answers immediately!"""