Clients keep the price they agreed to — always. New prices apply to your booking page and every new booking from now on. Hiding a service hides it from the page — nothing is deleted.
Longtime client at an old rate? That lives on her client card — tell me (“Chen stays at $120”) and I’ll hold it for her.
One-time discounts happen on the job itself — the accept card has an “adjust” for that. Quote-me services: they request, you look, you price — and her number lands on her client card.