I got this answer from coinbase
So my 300 $ bch wrongly send to my btc coinbase wallet can’t be recovered
Hello,
Thank you for contacting Coinbase. Based on the information you provided, it seems like you have sent a specific type of cryptocurrency to the address of a different cryptocurrency. Since Coinbase does not support transactions where one cryptocurrency is sent to the address of a different cryptocurrency, we are unable to recover these funds.
You can confirm this on your end by reviewing the addresses associated with your account here:
https://www.coinbase.com/addresses. For future transactions, please only send cryptocurrency to that cryptocurrency's specific address. You can always find the most current address associated with your wallet by navigating to the Accounts page and selecting “Receive” next to the cryptocurrency you want to use.
Regards,
Coinbase Support
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