MTN-MONDO Woes

You thinking you buying a from MTN but it's actually the company called Mondo.You receive your phone and discover that it's not the phone you ordered ,you return the cellphone within the specified period that you are allowed to do so. This was in July by the way and today I am still waiting for that contract to be fully canceled and get my refund for the debit order which they took without me even having the phone. So now to make the matters worse I am listed on ITC as owing MTN R15000 which is the value of the phone. MTN I don't know what is the right word/phrase to express my anger. MTN INTERVENE! And by the way there's a lady at MTN in Roodepoort by the name of Nthatisi she has been trying to assist me with this mess but her efforts are in VAIN.Thank you for your assistance Nthatisi so far let's see if my cries on this platform will yield any success.