Limit increase challenge and poor service

I’ve appalled by MTN service. I’ve been their customer for more 20 years with a contract, paying about R1345 monthly. I didn’t upgrade immediately when I was due for one and now they have reduced my contract limit to R345 and refuse to increase back. It’s been 6-8weeks of calling their call centre, going to their outlets with no positive feedback has received. Their vetting department is pathetic to say the least. Whilst the matter has been escalated by one of the outlets, no one calls back to give feedback whatsoever. They clearly have enough customers and don’t care about loosing one. Im ready to port to another service provider.