Contract fone

I would like to complain about Mr price because they offered me a contract fone of a mobile called Mint that goes with a smart watch....I took the contract fone but the fone do not even last a week after I recieved it and had a speaker problem, I called them and told them about this and they collected the fone, and they sent it back to me saying that they fixed it and the fone had the same problem again and I called them again to come collect the fone but they never came till now....and now they chase me with lawyers saying I must pay a damaged fone