A booster adds a block of extra chats to your month at a lower rate than paying chat by chat. It's a one-off charge on top of your monthly subscription, for that month only.
You don't pay per chat for anything inside a booster. The booster price covers the whole block, so the more of those chats you use, the better the value.
And if you get through your chats faster than expected, just message us and we'll move you up to the next booster for the rest of the month. You only pay the difference between the two, and the chats you've already used count towards the bigger allowance. Boosters run per billing month rather than carrying over, so we'll only ever suggest a size that fits your real usage.