You keep your credits when you cancel your plan. Because of this, we sometimes call it "pausing" your plan. After pausing your plan, you will not be billed again until you resume your plan.
Here's how to pause:
Go to your billing settings
Click "Pause"
A pop up will appear asking why. Select a reason, then click "Pause Subscription"
Your payment method will not be charged any more. (And you keep your credits)
If you paused, and want to un-pause, then click the "Renew" button at the same location.