Dead Television From PnP

My wife and I had bought 2x Aim 55" LED's from the Chatsworth Branch in April of 2019 , We had only unboxed it in August 2019 as we purchased a new house. However we have had a problem with 1 that used to go off on its own. I have been into the store on numerous occasions to complain about this but our receipt had been with my father in law who is now late. This tv does not come on anymore and the person that handles these queries from PnP Chatsworth cannot be contacted. This unit is under 3 yrs old and I have only used it once , it now hangs on my lounge wall not doing anything and i cannot get any help to sort it out. Model # CZ2055 - Serial # CZ2055A***5 . I hope to get some sort of help or they can have their TV back .