MTN and Summer trading -a lethal combination

I received an unsolicited phone call from Summer trading to upgrade my phone contract. When I received the contract docs via email, I decided against it. I logged the request to cancel the upgrade with Summer trading on 30 November- it was supposed to take 5-7 business days to take effect. After NUMEROUS phone calls to both MTN and Summer trading, as of 10 January 2018 no cancellation of upgrade has as of yet been effected. Summer trading's business address on their website is 2 years out of date, and they either don't answer their phones, or they put you on hold until you are cut off and no messages left for supervisors have been returned to date. So much for Summer trading.

MTN are taking the view that I must sort this out with Summer trading as it 'is not part of them'. To date MTN has not been able to explain how come they gave my details to Summer trading without my consent and hence breaking the protection of my personal information.

I think this is unacceptable.