Overbilling MTN contracts

My dad is a pensioner, and in Aug 2016 he cancelled two MTN contracts, however MTN kept on billing him up until today. He has gone into MTN’s shops and cancelled these contracts a second time, which again failed. Multiple phone calls were made and currently we have two open queries, one with Customer care and one with the Retentions teams which has been created early April which has gone unresolved and unanswered.

We are feeling so helpless as the MTN shops direct us to call centers we need to phone however these centers seem to be not competent in answering our queries and solving this problem. So more than 18months later my dad is still paying for two cancelled contracts. So frustrated as it seems MTN is dragging out this process and we are probably not going to get any of our money back which has been incorrectly taken for more than 18months, its really accumulating to a big amount.