I have a fear that I can make a mistake and it is nonrefundable in cryptos if anything goes wrong.
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I personally feel you are making a simple transfer to a complicated one. Do remember USDT is a cryptocurrency and you cannot transfer any amount to anyone unless the recipient has a USDT recieving address. Again a reminder to you there are different blockchains supporting an USDT transaction. Please do a Google search or a YouTube and you will find solutions related to your query.
Is there a reliable firm who can do that? Better in Euro zone. I will transfer USD funds to their bank account and they will send to AAAFX with USDT.
I cannot be certain if the firm is reliable. If they are offering you an unreasonable gain then they are not. If they are not allowing you to complete your withdrawal then it is not a good situation. Please reply more in detail, if you want to find out if they are genuine.