Yes. You can cancel your subscription at any time under Subscription settings. After you cancel, Protection stays active until the end of the period you have already paid for and you will not be charged again. When that period ends, Protection alerts are switched off and no longer sent.
A normal cancellation does not entitle you to a pro rata refund of the monthly fee already paid. This does not affect your statutory rights, in particular the right of withdrawal where it applies.
Cases you have already opened remain available in your account. If you have built up cases on the Case + Protection plan, they are kept for 90 days after the subscription ends. If you subscribe to Case + Protection again within that period, you get back the cases you had available.