How do I un-restrict my Apple Cash account after a mistaken fraud report?

You can certainly send Feedback to Apple here:

Feedback - Apple Pay - Apple

Whether it was a mistake or not, your account is a "risk" to GreenDot Bank due to that action. It is their choice to continue doing business with you. The same thing happens for users of the Cash App that is managed by Sutton Bank. The bank really does not matter and all of them operate under the regulations of the Federal Government, it is not Apple that makes that choice.

The correct action that should have been taken is to contact GreenDot Bank for an issue with that transaction, not dispute the charge with your bank. There is nothing Apple can do to intervene in any decision made by GreenDot and you can certainly suggest Apple use a different bank for their service, but the outcome would likely be the exact same, just like those users who had the Cash App.

I agree with Jim that unfortunately you’ll need to consider other services.

If Chase Bank is in your area, they have some great transfer services to other bank accounts. I used it for my children before there was an Apple Cash service. I set up scheduled transfers etc.

You should read some of the posts about Bancorp and Republic Bank that handle P2P transfers for PayPal. Green Dot starts to look like a saint.