When you sell a membership that has a contract period, the contract end date is set at the time of purchase. The contract end date specifies how soon a user can cancel the membership (though staff have the option to make exceptions for early cancellations if they choose).
Change Contact End Date
To manually change the contract end date for a users membership:
Search for the user and head to the membership tab of their profile
Click the three dot near their contact end date
Select the new end date and click confirm.
Please note: When you change a membership to a different plan the current contract end date will end and a new contract end date will be set based on the length of the membership you are switching to.