When a pledge is first placed it's actually considered a pending payment that will only be charged at the end of a campaign, and only if the campaign meets at least 80% of their total goal.
Because of the delayed timing of this process (if a pending pledge is placed in June, but charged in July for example), sometimes banking apps mistakenly detect a charge as a recurring charge, however our site doesn't have the functionality to set up recurring charges for pledges or tips. So your pledge is actually a one-time thing and you shouldn't be charged again for any reason.