There is no one you can call and the IRS will not tell you.
If your tax return is being rejected, then you will have to print and mail your tax return, claiming your dependent. If you are owed a tax refund the IRS will pay you the refund.
Within a year you and whomever claimed the dependent will get a letter in the mail as the IRS starts the investigation on why the dependent was claimed on two tax returns.
See this TurboTax support FAQ for printing a tax return for mailing - https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...
