Dumb question: how do you pay at Love's truck stop?

Most are set up to accept fleet type cards, not credit cards.

Most will have a phone by the pumps. Pick up the phone, and they will answer. Usually giving them license number will be all that is needed. Them them you are a RV. They may have you come inside before fueling, or may turn on pump, and have you come in after. Pull ahead after fueling, then go in. Let the truck behind you fuel while you go in to pay. If you want to stay a bit, pay, then park, then go inside.