MTN takes no responsibility for upgrades through third parties!

I thought I was contracting with MTN, even doing my upgrade on their website. But they farm that out to a third party and then take NO responsibility for it. I can't even cancel this contract within the 7 days with MTN. They tell me to phone the third party, who is impossible to get hold of. Go look at their T&Cs - its stipulated that they take no responsibility, although they send you there. WOW!!! So I'm contracted with MTN, but actually I'm not. I actually cannot believe this.