Wonga chief operating officer Niall Wass has urged the Archbishop of Canterbury, a critic of the firm, to try out the payday lender.
"What I'm asking him and others to do - go use the service. See if you think it's fair and transparent," he told ITV News Business Editor Laura Kuenssberg.
"Take out £10 for 30 days. Pay it back after a week - which you can't do in many other places. Look at the price, tell me if that's fair and transparent.
"And then judge us by our customers. Our customers are regular people."
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Guillier conceded a "severe defeat" defeat to his supporters as the result came in.
The outage struck Hartfield-Jackson Atlanta International Airport at around 1pm local time, stopping all outgoing flights.
It will be a chilly day for many parts with the highest temperatures, about 10 Celsius (50F) in the far northwest.