Going on holiday

Hello, my son lives in supported living and has 1 to 1 support from 7am until 10 pm and 2 to 1 support for an hour each morning and evening. He also has shared night time Support. He goes away each year for 5 days with 2 support staff who take turns during the night if needed. He pays for their meals and any entrance fees for activities etc. The care provider tell me that they use “banked” 2to1 hours (which accumulate over the year due to staff not being available at the time) in order for my son to have a holiday and to pay the staff for their extra hours. I’ve been told that due to these “banked” hours not being properly recorded my son is having to pay the shortfall in the cost of his holiday. Surely the care provider receives funding for his commissioned hours and shouldn’t be charging my son for their own ineptitude. Can anyone advise me please?