60 days with no response

I run a training company and have 3 MTN phone contracts and 2 MTN data contracts, my signal has always been poor but has become progressively worse, to the extent that my business is suffering, 60 days ago I complained to MTN who promised to respond within 12 working days, they did not. I have subsequently submitted numerous complaints to customercare@mtn, also complaints@mtn have called coverage on numerous occasions, have submitted 3 hellopeter complaints and have still not received one single phone call from MTN. All I get are the standard \we apologise for the inconvenience .... "responses. MTN simply ignore my 2 month old complaint! They must be the worst cell phone company or company that I have ever had the displeasure of interacting with"