How to get my money from these extortionist

I never signed up to take payments through QB. I invoiced a new customer and unbeknownst to me payment links appeared on rhe version of the invoice they received. Without proceeding down to my personal payment instructions my customers accountant clicked the link and paid Quickbooks my money. I have no bank accounts linked to my account because the fees for that service are astronomical. They want $898.71 as payment for a service I never signed up for, never inquired about, and never gave them permission to implement on my behalf. They say they are unable to send the payment back because I NEVER SIGNED UP FOR THE SERVICE. But if I link a bank account and give them the $898.71 that they are in no way entitled to they will give me the difference. They took more than 10% of my money from my customer. They say they added the service as a convenience to me!!! As a one time courtesy they will request that I be refunded the larger of the 2 fees as my customer paid both invoices at once but they won't give me the remaining balance of the fee they are trying to extort out of me. That amount is about 275.00. For a service I did not want in the first place. Not one of their people will guarantee me that I will be granted the "one time courtesy." One person did try to make it up to me by promising the difference in refunds to my credit card for money I am charged for my subscription until the smaller balance is paid. But that just ties me a thieving, unethical, company that I will never trust again at this point. Every time I call for help they just keep trying to sell me the payments service over and over. At least the lady I spoke with last admitted that this happens all the time. Does anyone have any suggestions? I refuse to be extorted by these people.