Battery Center Sold Me The Wrong Battery

2023 around June or July I bought a battery @ Battery center Welkom. I Did not come with the car because it was dead I left it in the garage, so I went to buy a new one because it was recommended by someone I know. So, they asked me the make and model of the car, which is a VW Jetta IV 1.9 TDi diesel car, they checked on their system which battery is best for that car. After they gave me the which wasn't the 652A - 658A battery it was less and I asked them if this was the correct battery and they said yes. I was assisted by an African woman she said that I can bring in the old battery so that she refund me that discount we get when buying a new battery.

Fast forward to last year July 2024, the car couldn't start in the morning because a diesel car during winter uses glow plugs to ignite the engine and that consumes a lot of energy from the battery alone, I then took the car to battery center Klerksdorp because my job transferred to the North West, battery center Klerksdorp checked and tested the car, the Alternator is 100% fine they assumed the battery is dying slowly because it is too small for my engine especially during winter and I should take it back to Welkom because it was still under the warranty period.

Battery Center Welkom then took the battery after they did the testing and they discovered that the battery is dead. After some time, they said this battery is too small for this car, I asked them to give me the correct one and they could not, they provided me with the new same battery around October 2024 and fast forward to April 2025, the new battery starts giving me problems and i am suspecting that it is dead now.

Please advise me on what to do now again.