The Stripe one time charge trigger is always associated with the stripe integration in the Agency Settings!
Please note: a card has to be set as default in stripe for OTC to work
https://www.loom.com/share/eecc2601a84842c98f8aafd0be7a725a?sid=49e031ce-af23-42e6-9fd0-f0e23b9b19d7