AuthNET payment plugin fails to use invoice prefix

The invoice prefix is set on my site, but all invoices come through Auth.NET prefixed with the default "DC-". Looking at the os_authnet constructor shows it calling the invoiceNumber function with no parameters. The invoice prefix setting needs to be loaded in here, but I'm not sure what code to use for calling it... Any help?

Hello Chad,
Can you please submit a new ticket to EShop category to send me the your site information so I can check and get back to you there?
Sincerely, Giang