I just realized that my son does not have to file taxes because he did not exceed the threshold and we claim him as a dependent.....but I already paid turbo tax

Does he have a W-2 that shows tax withheld in boxes 2 or 17?  Even if he does not have a filing requirement he can file to seek a refund.    Or....if he has even $400 of income from self-employment he is required to file and pay self-employment tax for Social Security and Medicare.

No one in the user forum can resolve a billing issue.  If you have a question about your TurboTax fees or billing, make sure you use the word “billing” in your request for help.  Do not use the word “refund.”

https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number