Bad Service

I have taken a contract with Telkom mobile online for a Samsung J7 Pro, itr arrived on the 1st Feb 2018. once I opened the goods after delivery, I realised that the buttons were not working. Took the phone through to Telkom Rosebank, where I was advised they couldn't assist me since the application was done online and was asked to contact the sales dept. They said the Phone would be collected and assessed, and a new phone would be issued, till today, I have been calling them to collect the phone, I am being taken from pillar to post, but no one resolves my issue. I am gonna be debited this month end, for something that isn't working. I want to cancel the contract, give them their goods, and have nothing to do with Telkom Mobile.