MTN - Atrocious and totally inefficient service

The contract for my late husband's cellphone and mine were both under his name. I have tried on and off over the past 2 years to cancel what is a month to month contract. I have persisted since July this year to achieve the transfer to Prepaid as I don't want to lose my number. I have had assistance from Managers of two MTN stores. MTN confirm they have the correct documents, i.e. Death Certificate, I/D books, Letter of Executorship. I am joint Executor. I have sat on the phone for hours, sent multipal emails but still they don't act. I am still paying for two phones. This is upsetting and disgusting service. Where do I go from here.