Unsatisfied payment

Hello! I write this review about unsatisfied payment I made to Markham GIYANI where I bought a phone on the 5th may 2020. The phone had a problem of overheating and draining it's energy so fast, I then took it back to the store where I bought it. The said the phone is having a battery problem where they charged me R300. So I want to know if I have to pay the money meanwhile the phone is having a warranty. Because it might be factory problem.