Is there any options to update Bill To and patient amount to 0 for existing charges?

Yes, this can be done through Change Bill to for patient transactions page.

Navigation: Specific Activities - > Change Bill to for patient transactions

 Brief Explanation: This page will help to update Bill to for patients. Date range, Patient Number or Account Type is required to be entered for Update. User can also update Patient amount to 0 from this page. At a time 5 patient data can only be updated. If Account type is selected than all patients under that account type data will be updated. For date range all transaction within the date range will be updated. Only the CO Type charges will be updated. User can also update patient amount to patient balance amount by selecting Patient amount drop down as Actual balance. If override patient amount checkbox is checked than amount will be updated for all the transactions as per applied filters. But if checkbox is unchecked than only patient amount with 0 will be updated. Update patient amount is insurance had paid or insurance has credit if the checkbox is checked than transaction with ICR and IP value will be updated with actual balance patient amount.