Shocking service from MTN... 1 week and still no sim swop

My phone was ****** last week and my contract with MTN is through a company called RMCS. RMCS have been trying to access MTN to get my sim swop and conversion done to no avail. According to communication from them MTN do not respond to their requests timeously! I think this is absolutely appalling given that essentially I am still an MTN customer and made numerous trips to their store to get this sorted out and was told they can’t do it and RMCS need to assist but when they try MTN refuses to assist. Bottom line is that an MTN customer is suffering for over week! This is absolutely unnecessary and makes me realize that if this is ever sorted out I seriously need to consider leaving MTN as a service provider!