Unprofessional service

Terrible service at Ackermans. I’ve bought a phone a Samsung A10 being just 6months old and it isn’t working. I went to Ackerman’s I have proof on bank statements as the phone was bought on credit card however they do see purchase on system and the manger refuses to authorise anything. I bought the phone for my mom who is 60 and since recently the phone has been giving problems and it’s fairly still not a very used phone.