I took a phone on account in January this year 2025

I took a phone on account in January this year 2025. I experienced the problem with the phone i then reset it not knowing that it will shutdown. I had to take it back to be fixed by them, I then received a call today in the afternoon where I was told that I have to pay them R300 something so that they can fix it for me. The unfortunate part is that I was not given the copy of the contract.