Mobile device lost in the store

I purchased a phone for my uncle in May, same month the phone gave me problem and took it back for repairs... Till date the phone is nowhere to be found... None of the consultants not technician are able to trace the device... I have requested a form of communication via email that tracks the phone but there is nothing like that. May I please be credited back the purchase amount because my uncle hardly used the phone and it's been 5 months without the phone