Testing a price rise on the next 20 new members only

I'm not changing the price for anyone already inside — that feels like a separate question and I don't want to mix the two. So the experiment is narrow: the next 20 people who join get quoted the higher number, nothing else about the offer changes, and I track how many actually complete. My hunch is the follow-up is the real problem, not the price, so I'm going to check that first before I blame the number.