Accidentally sent Ethereum to an ERC-20 address.

Hello, please help I am losing my mind. I sent a couple hundred dollars to a website that is very well trusted. Thousands of five star reviews online. They have a disclaimer which says to send ethereum "normally" and has in parenthesis "ERC-20." I did my research and saw that ERC-20 wasn't a separate coin so I sent the money. They are now telling me these funds are unrecoverable because I needed to send ERC-20. Ok, I made a mistake, its actually a whole different thing but how in the world am i finding almost no one else on the internet who has run into the same issue? I didnt think I messed up that bad. I don't believe them that it is unrecoverable but does anyone have documentation to prove this? I have seen a lot of posts saying that they accidentally sent ERC-20 to a normal ethereum address but not the other way around. Any information would be appreciated as I have done a lot of reading and I still don't fully understand what ERC-20 and how It could be so easy to just lose my money like this. Thanks

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EDIT: ok i realize the problem isnt that its ERC-20 or not but thats what the website claims.

this is the response from their support team

Your payment was processed via contract:

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This is why we are unable to process the funds and you do not see the funds, as the payment was not processed.

It is stated on the deposit page not to send via contract payment. (it says send it "normally" btw)

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I didnt send wrapped eth.

I sent it using coinbase.

i have the etherscan to prove it was succesful.