There are different ways to suspend subscriptions, either you can manually mark them as suspended or
enable a profile-option to automatically suspend and resume a subscription according to the state of the agreement.
Using our api, it is also possible to change the state of a subscription.
It is not possible to change the state by importing a file.
Click on the subscription to open the details. Here you have a suspend button.

When you edit a suspended subscription the state is not changed when confirming the changes.
Reactivation is required.
Future transactions for a suspended subscription are placed on hold.
Once you resume the subscription the next-run is calculated based on the recurrence and start of the plan.