You can easily change the status of a membership to For Sale or Not for sale so that you decide whether customers can buy the membership going forward or not.
Please note that marking a membership to "not for sale" will prevent not only customers buying it but also you selling it to them on their behalf using your business account too. Any existing customers who already have the membership, however, will continue to be able to use it.
To change a membership status head to Memberships >> select the membership you wish to edit. Next, click on the "Edit" button on the right-hand side within the General section and change the status as desired:
Finally, click Save at the bottom of the page.