Very poor customer Service

Berea Battery centre ,Durban. 12/05/2020, I went to this place for my car battery problem, the guy tested the battery and found 1 cell to be faulty so I had to change the battery, but it was still under warranty as it is 23 months old and I bought it from this place on (23/06/2018) but I had lost my receipt and I only had my bank statement reflecting the transaction made the day of purchase with the name of the retail but the guy said he can't assist me because the store is under new management so this problem falls onto the old management, then he just left me