Team Forms uses your existing Microsoft Teams groups to control access to forms. If you would like to remove a users access to a Team Forms instance then you will need to remove them from that Microsoft Teams groups. This can be done in the Microsoft Teams UI using the steps outlined in this article.

Unfortunately, you cannot simply remove a user from Team Forms (but not the team) so that they are not included in the monthly user count. Any user who has accessed Team Forms that month will be counted as a user for licensing regardless of if they submitted a form or weather they have since been removed form the team. This is unfortunately no option to remove them for licensing purposes.