Bad Service

I’m not happy with the service I have been getting from PEP regarding a problematic cellphone I bought from their store, I got the phone in April 2019, and the first issue I experienced with the phone is that it got burned at the back whilst charging. I returned it to the store, it was taken in for repairs, the feedback was that I must be given a new replacement phone (no detailed explanation was given), I then proposed that I must pay extra to get another brand - I was told it’s not possible as per the company’s policy. Apparently they need to replace the same product 3 times before they can allow you to do an exchange in a form of receiving a voucher (which will allow me to get a phone of my choice) - This happened in June 2019.On the 4th of December 2019 my phone refused to charge again, I took it to Pep on the 5th, it was booked in for repairs, yesterday I received a call to come and collect the phone, when I got to the store I was given back a phone which does not charge and switch on. There was no detailed report instead I was told to charge it for 6 hours (it still does not switch on), I just want to be allowed to get a different product or a refund.