How do I get hairspray off my bathroom wall?

I would suggest to try alcohol

OK this may sound dumb but I don't use hairspray,if it washes out of your hair with shampoo then have you washed your walls with the same shampoo or a clarifying shampoo?

https://housewifehowtos.com/clean/how-to-remove-hairspray-from-walls/

White spirit and elbow grease - that’s in English! If you’re in the US, roughly translated I’m saying paint remover and rubbing, but if the wall is painted, try it in an unseen area first and VERY GENTLY rub!

Vinegar & water & spong... OR... I know this sounds silly, but SCRUBBING BUBBLES works on most everything in the house (including smoke-grease/grime from the nicotine).

Shampoo, keep it simple, it's what you use to get it out of your hair

After being a hairdresser for thirty+ years I can tell you shampoo will take off wall, but if have build up on flooring an ammonia mixture is your best bet.

A magic eraser will take it off with very little work. They work to clean practically every surface and any type of build up.