You can submit your suspension request at any time but your suspension can only be scheduled for the start of the next calendar month. Please note that if you’ve already suspended your number previously, you will need to have completed 1 billing cycle before you can submit another request for suspension.
You can schedule the suspension of your number up to 6 months in advance and you can suspend your number for up to 12 months.
To find out if you can suspend your number, head here.
Suspension of a number is only available to those on the $28 /mo Base Plan.