Product: Money transfer, virtual currency, or money service

I withdrew $XXXX from my XXXX account and sent it to Coinbase via the USDT transfer method.  Coinbase received the $XXXX and it showed complete in the XXXX system.  I contacted Coinbase with a support ticket and was pretty much told I was out of luck.  XXXX says CB has my money, CB says they can't accept USDT but they didn't reject the transaction...they accepted and now say they can't return it. Regardless of they XXXX explanation I have found comments from people online (coinbase employee) that say with the right key they can return my money.  This has been happening to people for over a year and neither company has done anything to fix this from happening in the future.  This seems like a scam and their material didn't explain this would happen very well at all they both just let the transaction happen only later to tell me it's gone... This isn't acceptable to simply have your money stolen like this...CB has my currency regardless what they say..  

Here is their response: XXXX XXXX XXXX  |  XXXX PDT 
XXXX replied:
Hi XXXX,
USD and USDT are not the same thing. USD is the currency controlled by the United States Treasury. USDT is an alt-coin built on the Bitcoin blockchain. Unfortunately, our key-signing mechanism is not equipped to handle alt-coins that run on top of digital currencies such as bitcoin or ethereum. The security and integrity of our private keys is of the utmost importance to us. As a result, the specific private keys associated with an address are not physically available to any single person. It would take a massive effort and some very large engineering resources just to access a specific key, not to mention the inherent security risks involved. Heres an analogy that might be helpful:
Imagine someone wrote you an IOU for $XXXX on a $XXXX bill. You then put that $XXXX bill in a change machine by accident. Since the change machine doesnt have any way to read the IOU printed on the bill, it gave you four quarters, the face value of the $XXXX bill.
USDT is like an IOU written on a very tiny fraction of a bitcoin, the USD value of which is usually only a few cents, if its even that much. So what you sent to your USD wallet wasnt USD. It was the very tiny fraction of a bitcoin with an IOU for whatever amount of USDT you had in your USDT wallet.  When bitcoin is sent to a Coinbase USD wallet, we attempt to convert it instantly into USD so we can deposit it in the receiving accounts USD wallet. If the tiny amount of BTC is less than $XXXX, were not able to convert it, but if we are, we deposit the corresponding amount of BTC in the receiving accounts BTC wallet.  Unfortunately, unlike a coin machine where you could hypothetically find someone with a key for it who could open it up and retrieve the $XXXX bill with the $XXXX IOU written on it, our systems security is designed so that no one is able to do that. No one is able to get into the back end of the system, because if we left an opening, all our funds would be less secure.This is one of those things I really wish XXXX would make clearer to their customers, that USDT is not the same as USD. Unfortunately, there isnt anything we can do to retrieve those funds. Theyre locked up tight. Im so sorry for the inconvenience this has caused. I wish I had better news for you!
XXXX 
Customer Support 

** When the BTC transaction error appeared on my account (system was confused and tried to deposit