You mean you've contacted both supports (Binance and Stake) and they said they have no access to your USDT? If that's it, then it is what it is, the funds will prolly be stuck forever, you could drag them out on some of their online handles and see what that gets you.

That being said, you should not use custodial wallets and if you want to, you have to be very careful with them, cross/double check the address before you send funds to them, when you have issues with custodial wallets, only the support (third party) can help you, and they are more often reluctant to help.