Phone repair

I need to report bad service from Jet Stores-Empangeni my nephew took his fone for repairs its been over a month and we've been in & out of the store nd this lady by the name of Phila jst look @ the receipt/invoice nd said the fone is nt there without even checking @ their draws, this fone is 12 month guarantee ,,please i need management to look at this matter asap before taking further steps,, they dnt even call the client to aknowledge the delay frm their side nd im nt sure how they we goin to call him since they took his cell no.to call him ,,,,