Teller raises $4M to take on Plaid in the U.S. by providing API access to bank accounts “They’re idiots, they’re really naive,” is how Stevie Graham, the co-founder of fintech Teller, once described Open Banking Limited, the body charged with delivering open banking in the U.K. His view back in 2017 — which now looks somewhat prophetic — was that open banking wouldn’t be the competition driver it was hyped up to be.