subscriptions can be changed or cancelled at any time. for per month subscriptions, unless instant billing is enabled, you will not be charged for the month in which you cancelled. for per-bake subscriptions, you will only be charged for the bakes that were completed while your per-bake subscription was active
for example, let's say you start a new monthly subscription on the 6th of the month. if you then cancel your subscription on the 22nd of the month, nothing will be charged. if instead you keep your subscription into the following month, you will be charged for that first month's subscription. and yes, we do monitor for users who abuse this policy, so avoid a permanent ban and play nice!
in the case of a per-bake subscription, let's say you also start on the 6th of the month. since this type of subscription only accumulates payments when your baker bakes a recipe, you could cancel at any time and not be charged anything if the baker did not bake anything while your subscription was active. if, however, the baker bakes a recipe on the 21st of the month (for example), and you decide to cancel your subscription on the 22nd of the month, you will be charged on the first day of the next calendar month for the prior month's subscription payment (in this case, for the bake on the 21st)