Bad service

I hired a vehicle on the 27 January 2016 at 10:40am and i was told that i can return the vehicle within 24 hours and of which all was okay, i was also told i cannot fill the vehicle petrol anywhere else but only their specified garage next to them. When they were booking a vehicle on the system their system wasnt working right up an down and i had to wait and wait until they got it right and i didn't complain about my time. when i took the vehicle i returned it the following day just 40 minutes late at 11:20am and they saying they will charge me the full day agian coz i was late in 40minutes just imagine, while when their systems was giving them issues i didnt say anything. they refuse to bill me per hour, they just wanted me to pay full amount for the next day and they insisted including the management and of which i didnt need the car anymore. Stay away from such companies they only focusing on making money and they dont care about their customers.