i verified myself at the basic level and i am now allowed to do digital token trading. in order to do fiat and margin trading i need to verify myself at the enhanced level, so far that's clear. but i don't see any fiat trading possibilities. i only see usdt. does usdt trading fits into the digital token category that i can trade with basic verification, or is this the fiat trading that is being referred to that i need to get enhanced verification for?