Horrible purchase experience

I bought a Play Station 4 at cash crusader Pretoria North on the 30-09-2022, it was a ITB PS4 at R4599.90, recently my kids are downloading a lot of games and it was running out of space, so went into the settings to check the storage and realize it was 408GB on this PS4, so surprise I took it back the store to complain. They told me they can't help because the warranty has passed, but things got even worse when I they check my slip, the serial number on the device is not matching with what is on the slip, they told me it's not their device, I got the shock of my life because I only have this device, which I bought from cash crusader in Pretoria North. I make them to check the serial number on the device on their system, and they could find it as one of their stock, how this was sold to me they can't explain. The serial number on the slip shows on their system as sold but the serial number on the physical PS4 shows on their system as not sold. Now I have a device with serial number not matching the pay slip, this is horrible.