Depending on the country in which you use FREE NOW, there could be an authorisation of the estimated payment amount upfront when you try to book the service.
A pre-authorisation is a temporary hold of funds on your bank account or credit card.
This is used to ensure that the payment method is valid and that there are sufficient funds available to pay for the service requested.
The pre-authorisation is not a charge, but a temporary hold, meaning that the funds held will be released after a short period of time. Depending on your bank, the release of this pre-authorisation back into your available balance can take up to a week.