Game sold me a faulty phone

Bought a Nokia onthe 07 july2018 and used it for a month then it started giving me sound problems took it back to game then it was booked for repairs, phone worked for a day then started giving me the same problem again took it back again and they said they can't exchange it for me coz I've been with the phone for three months already I don't know if it's fair for them not to exchange the phone because it never worked after repairs