They work with Deltec Bank.
https://tether.to/en/tether-banking-relationship-announced/
From https://www.deltecbank.com/2022/09/01/the-history-of-stablec...
> Tether
> Launched in 2014, Tether (USDT) came to extraordinary success with a current market capitalization exceeding 67 billion USD.
> This stablecoin fixes the issues inherent in the previous three. It relies not upon volatile reserves or the idea of persistent arbitrage trading, but on hard reserves of fiat currency. For every Tether coin in existence, there is one US dollar in a vault backing its existence.
> In this way, the stablecoin handles a complete theoretical rout with ease. Tether continues to serve the burgeoning digital asset space while garnering the implicit affection of regulators.