Amended booking - money taken from guest at original booking date

[Sarah3431]

I have been contacted by a guest who has amended a two week stay to next year due to COVID. The remaining 50% payment was taken from his account, a whole year before the booking will now take place, without any warning. 
I believe Airbnb are wrong to do this. They now have 100% of his money when the contract he signed up to was a 50% payment at booking, and the remaining 50% 2 weeks before check in. 
He is arguing with them but they are refusing to refund him. 
I was just wondering if anyone else has had this problem reported to them.