Replaced My New battery with a small one

I sent my VW Polo to Auto Bonn for assessment, my car returned with a very small battery a brand i saw for the first time, a ***ukama one, its so tiny, that you cant even use a battery catch. I called them up and the attitude was bad, they guy said I am accusing him of *****ing, and said go and report to the police. But its a fact that its not my battery