Well, maybe I’m misunderstanding here. What are you meaning by
What are you charging another card for? If you’re being the middle man, why not deposit the money from your Square account into your bank, and then use your bank (or, any other third-party, like the Cash App for example) to transfer the money to whomever you need to? There’s no way, within Square Seller accounts at least, to transfer money from one account to another even with fees.