How do u buy a new phone n keep taking it to Repairs cell C

I upgraded my phone in December n in July it didn't charge properly n I took it for repairs again in Nov its was not charging n I took it for repairs it worked for a week I'm back to the same problem again. I think I got a faulty phone n now I call repairs they tell me to book it in again. I'm still paying for this device and have a long way to finish the contract. This is a raw deal