Sixt complaint: MIsleading Booking options

I was in need of a van for 1 day (9am Saturday 26th Nov – 27th Sunday 12:30).
i was quoted £100.

upon picking up the vehicle not a single person informed me that the booking for return didn’t appear correct (as it was 12:30 am – midnight!) to which the site does not open until from 8am to 1pm on a Sunday (in-fact every day they open at 8am).
it is physically and systemically impossible to return any vehicle at midnight although their website allows you to select the option.

the site should only allow you to select a time window from open to close based on the branch selected.

i am now being charged £287 because i had returned the vehicle at 12:30 pm (to which i had wanted to select as its just before the branch closes on a Sunday).

Further to add to this, I have just checked the website to book a van for Saturday 9am until Sunday 12:30pm and the charges are £118,
The charges you have pushed to me are not right.