Upgrade Botched by MTN

As a last resort I have to try HelloPeter as MTN simply ignores emails and do not respond to phone queries I logged. I upgraded end August 2018 to take advantage of a special promotional data offer that came with upgrading a contract. MTN does not do upgrades, they simply farm it out to Contractors, in this case CCI. After many phone calls between me, the contractor and MTN, the upgrade was eventually done. After receiving the new SIM Cards (yes two), I phoned MTN and they confirmed that the promotional data was not reflecting on their system. MTN said I have to Call CCI. CCI said I have to deal with MTN. I them phoned MTN Cancellations and requested to cancel on day 5. Now, almost two months later, the upgrade has still not been cancelled. Now MTN simply ignores emails and if you do speak to them, advise that I should have cancelled the upgrade with a company called Velocity. I never dealt with or heard of Velocity before. Despite sending emails to three different email addresses of various people / department within MTN, neither of them respond. I have called numerous times since the cancellation was requested, but those I managed to speak to only promise to escalate the matter. Nobody ever calls back after these ‘escalations’. If you insist to speak to a supervisor, they’re always busy and I get cut off eventually. Does anybody have any suggestion how to get this resolved? Or is the Consumer Goods and Services Ombud the next step?