Samsung — unsatisfied products and services

Sir my sister purchased samsung a50s mob as on 20 oct 19 (Bill attached). After 6 moth it showing problems. First time phone stopped working and send to service center teleriksson gallary faridabad haryana, they update software. Second time stopped working and send to the same they said mother bd faulty and replaced... Thn the last time (Complaint no [protected] dt 18/8/20) deposit the phone to them. I contacted your customer care no and they said the buying amount will be returned in 15 days.. Now the teleriksson gallary says a 22990/- purchase coupon can give us to purchase samsung products... I am totally unsatisfied with your products... So i need full refund as cash not purchase coupons... Thank u