OfficialPayments.com Customer Service Issues

After paying $[redacted].00 and a $2.00 fee to OPC from my credit union checking account, an additional $[redacted].00 was withdrawn from my account by someone at [redacted] Constitution Ave, Washington, DC. This caused an overdraft and impacted my ability to pay for my health and life insurance. I have tried reaching out to the IRS without success. I am retired and on a fixed income. I desperately need assistance to resolve this issue. Please provide a phone number for OPC so I can speak to someone directly. I have automatic payments set up with OPC until November [redacted]. My contact information is as follows: Michael L. Schnabel, email: [redacted], phone: [redacted]. Thank you for your help.