Europcar hire - Courtesy car

On the 8 July 2023 I went for a courtesy car to Europcar in Hatfield, I inspected the car with the guy who's working there the way he was inspecting it since it was my first time to take the car from them. On our inspection we checked the exterior of the car which is the body, windscreen, front bumper underneath and back bumper underneath as well as checking if the spare wheel, jack and wheel spanner are there, everything was there and we also check the tyres
I didn't see anything wrong with the guy because he's the one who was checking these things because he knows how to check and I didn't really know what to check exactly

The car was due to go back to them on the 7 August 2023 at 13:12 time and I took it back on that day before the time stipulated. The other guy checked it again in my presence and on his checking when he opened a boot to check if the spare wheel, Jack and wheel spanner are on his opening right exactly where you put your hand to open the boot on the bumper there were 3 lines which he said that was a crack I told him if it's a crack that means I found the car with it because the time I've been using the car I'd never notice such since it wasn't something really clear to me, and that wasn't much of an argument between me and the guy. He then brought a book to write on, I asked what should I write on that book? He said I must write how the car kept me while it was with me. I then wrote " since the car was with me nothing happened to it and it has been with me for 30 days, on top I wrote my details which is my names and surname, address, I'd number and cell phone number. After I finished writing all those things he wrote the details of the car which is a make and registration and colour of the car, I didn't watch him while he was writing these things and also remember since it was my first time dealing with Europcar hire I didn't know if there's anything one should write as a receipt of receiving back the car so I did this comfortable because I knew nothing was wrong with the car since I cleaned it a day before the day of it's return. Only to find that what I filled was a motor incident report and I already signed underneath what I wrote. The guy told me I must leave they will pay my deposit into my account. The 7 August was on Monday I thought my deposit will be paid into my bank account before the end of that week since I wrote my banking details the day I went to fetch the car. Until Friday of that week the money was not reflecting in my account, I gave them a call on Friday asking when are they going to pay my deposit it's when I heard that I will not get my deposit back because I returned the car with a crack. I asked which crack and where was it they said on the back bumper which is it's those 3 lines the guy mentioned to me on the day of returning the car to them which I didn't know and on top of that I still have an outstanding amount which is due to be paid by me since their access is R4850 and my deposit was R2000 which I left to them and it was refundable on the day I return the car. Now they hold me accountable of the so called crack which I don't know. They say it might be another car bumped to me on my absence or I bumped the wall while reversing the car of which the car was not even bended the time I returned it back to them because to my understanding if there could be a car bumped to that one on my absence or I bumped a wall the bumper should be bended as well of which it wasn't. They don't want to return my deposit instead I have an amount that I have to pay on top of that deposit which they kept onhold