Momence allows you to freeze customer's subscriptions immediately for an indefinite period or schedule the freeze. You can even schedule when you would like the 'un-freeze' to occur if you have that information on hand from the customer.
Note that freezing will cancel the customer's future bookings made with this membership.
When a customer needs to freeze their membership, you can do this by clicking: Customers > Customer List > from Overview locate the subscription and click the dropdown menu to the right > click Freeze
In the pop-up that displays, you'll find options to freeze now, or schedule the freeze for another day. The second row will allow you to schedule that unfreeze date if you know it.