If you follow this link, you can cancel any paypal subscription. Note that a subscription is an agreement between you and Paypal – hence I cannot cancel a subscription for you!
You cannot reactivate your paypal subscription. In case you cancel your subscription you can however still manually prolong/renew your account here for a number of years you specify: http://openmtbmap.org/support/membership/
So follow this link, login to your paypal account, login, and you will see a list of all subscriptions you have, and cancel the ones you like (note following this link is the same as logging into your account and then go to "My Preapproved Payments" from within your paypal account):
This is how your subscription will look like:
You need to click on "Cancel".
Then you will be asked to confirm cancelling the subscription – after you click on confirm – the action is not reversible. You cannot reestablish the subscription.
You can if you like however still prolong your account by paying for fixed term extensions here (you need to be logged in) – http://openmtbmap.org/support/members/ :
If you see this notice on following the first unsubscribe link – then you have no active subsciptions (if you are sure you didn't cancel yet – check that you logged in using the right email):