Fraudulent van hire

Hi

I recently hired a van for a freind and at the end of the hire I was asked if I could hire a different one from the same company.

I refused to re hire the van as it was just a favour to start his business with.
I have recently had a bill from Salford for nearly £1000 from a different vehicle to what I hired.

My question is how can someone re hire a van in my name when I wasn’t present?

Surely a signature is required?

There fore am I liable for this bill?
Or is it a type of fraud? Or an error on the company’s side?

Thanks joel