He was offended at being labelled a "deadbeat" -- a term they use more than once -- and then a company wrote him a letter saying he never borrowed from them (despite the paragraph before saying he did, in fact, borrow from them [edit - my misreading on that. He doesn't know who he borrowed from]). Okay.
This was a company/group trying to criminally defraud people. Even in the legitimate debt realm there are criminal tactics to attempt to recover debt, usually after it has been written off and gone through multiple hands. The whole debt industry is a scumbag, shady industry, preying on the vulnerable. The debt/credit industry has an enormous number of punishers, from credit scores that can prevent you from getting a job to court-ordered remedies. They don't need the lobsters repeating their nonsense.
You misunderstood that paragraph.
He got a payday loan from an online lender, and paid it back promptly. The online lender was not Vista, the company to which his alleged debt purported to be owed.
*edited so I don't end a sentence with a preposition. I have no idea how by that slipped me.