Contract upgrade

I recently app**** for a mobile upgrade, waited 2 weeks with no follow up from the telkom agent. Phone was in stock but it comes with a memory card which wasn't available. I went into the store and was advised to take the Huawei P10 instead because they were unsure as to when they would get stock of the memory card. I took the P10. I get home charge the phone and it immediately starts freezing and heating up. Not even a day old. I go bk to the store and was advised that I can't cancel my contract and take another device even tho this one is defective. U will have to pay for the full contract. This is unacceptable as I had been advised by the agent serving me that if I have a problem with the phone within 7 days I can bring the phone bac**** So now what do I do for the next 24 months???? I am extremely upset