Hisense TV freezes abd thry refuse to honor their warranty to fix any TV over 50 inches on site fix

We have been struggling since November with a TV that keeps freezing and has to be factory reset every few days, Mahlubi solutions was send out then they blamed the remote, so we bought a new remote, guess what two days later same issue, we logged a call again, then the main board was replaced and behold 2 days after the TV freezes again, twice we logged calls now again and then Hisense opens a ticket wnd then shortly after it gets closed as customer cancelled, why would we log a call and then cancel for an ongoing fault that is not being sorted, they are running away from their responsibility to cover their warranty, please assist in having the issue resolved as I'm seriously thinking to take leagal action now