If you remove that user from their seat, they will no longer have access to your account.
The great news is you can invite another teammate to fill that empty seat.

To do this, simply navigate to your Subscriptions Tab.
Then, find the user you'd like to remove.
Next, click the three dots across from their name and select Remove from Seat.

If you no longer wish to use the seat, you must cancel the subscription. This will prevent future subscription charges. Learn more here.