Charged for an upgrade I didn't ask for!!

I booked a small car I can afford via Vitality. If I get to the venue and I am upgraded, why did no one explain that I will be charged differently? I was under the impression that the deposit is the only difference.

Firstly, I booked a cheaper car and when I got there it was given to the lady that was helped in front of me despite my booking. If I am given a different car, the assumption is that I am upgraded for free with all the other conditions of my booking remaining.

The comparison of my booking with the invoice is **************** and is distasteful at the very least! This was not what I was expecting and definitely not what I budgeted for!!! I didn’t ask for this car, it was just given to me and nothing else was explained.

You can’t just upgrade me without explaining anything as if I made my booking without being influenced by my budget! In this economy??????

I sent an email to customer service and I was ignored.