Query about a phone

I bought a phone at pep I took it for repair twice and it's for the third time and it's still doing the same thing and they are not willing to give me a new phone it's been 3months since I bought that phone,their manager sad she will look in to the matter I'm still waiting and still not happy about their services I feel they have sold me second hand phone please intervin I really need help pep it's not a good shop at all