Bad service : wrong battery size

On the 25th of November 2018 i bought my battery @ Battery Pro that was baised @Centurion next Gautrain. At the beginning of 2020 March the battery started giving me problems. I went to Battery Pro that is now @ Wierda ParkCenturion. I met the guy who sold me the battery . The guy make me to wait . He took the machine & tested the battery & acknowledged the battery was dead he left & spoke to his manager & come back saying the car was having electrical fault, he insisted that hi should take the car to auto electrician. I took my car to Mazda they did the diagnosis & there was nothing wrong with the car. I went back to Battery pro telling them there was nothing wrong with the car the battery is dead the guys give me an attitude I am not sure if this was done because i am a woman or the attitude was given because of my skin colour. I took my car to be checked by 2 auto electricians they still insist that the problem is with the battery not the car because a wrong size was fitted into the car.