Bad service - Take-a-lot voucher not working

I upgraded my contract on the 5th September and was a supposed to receive a Take-a-lot voucher, consultant gave me the pages on how to redeem the voucher. When I sent the IMEI number, it said it is incorrect I must try again. I triple checked it and it was correct, the consultant told me that I should try again, then I sent it again and the sms I got back said that it had already been redeemed, but it had never come through to me. I have emailed her on the : 6, 9, 11, 16, 26 September and today 1 October, and the response I keep getting is that she is following up but receiving no response. This is really PATHETIC, how hard is it to get a voucher? Now she says that it is through Samsung, but it is a promotion that MTN is offering. This is very disappointing service through MTN!!! How is the consultant supposed to offer good service if she is not getting assistance with problems?