This does not cancel your subscription, it just disables the card.
Instructions how to disable/enable a Stamp Card:
Login to your Merchant Console
Select Stamp Cards from the red left hand menu
Select the stamp card you wish to disable/enable, by clicking the relevant tab under the page heading. If you only have one stamp card, you do not need to do this.
Select Edit details from the top left area
Toggle settings to either Stamp Card: Live or Stamp Card: Disabled
Press Save & exit to save changes
Changes are applied immediately to the Stamp Me App, but you may need to exit and reopen it to refresh it.