Signing approval permissions

Hi, please I’m confused why I’ll be interacting with usdt smart contract, but when calling the approve function, some wallet like trust wallet or infinity wallet charge in bnb instead of usdt or eth, please why is that and how can I make them charge in one token?

I don’t understand what that means. How does it change it to bnb?

Only metamask shows the usdt but trust and infinity wallet shows bnb, is this a problem or its just what the wallet charge in?

It may be only the gas fee that needs to be paid for that transaction

Thanks you for your reply