I was sent a 1099-NEC and filed my taxes already. I was just informed that they made a mistake and it should have been a 1099-MISC. What do I do now?

The return cannot be changed at this time, and you should wait until the return is either accepted or rejected.  If your return is rejected, you will be able to modify it before you resubmit.  

If your return is accepted, you can amend or correct your return if there is a corrected Form 1099.  You will want to wait until your original return is processed.  Sometimes the IRS makes adjustments there, and you do not want two versions of your return in process at the same time. If the amounts in the form are the same, it might not change the numbers in your tax calculations. The IRS might process it as it is. Or they might send a letter asking for additional information.

There is no additional charge to use Turbo Tax to amend your federal or state return. Many, many people have this happen every year. It is a very common thing to have a late or corrected form and need to file an amendment, for federal and/or for state.

Below is a Turbo Tax FAQ with step-by-step instructions to amend.

https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-filed/00/25588

Tax year 2021 federal amend form should be available by Feb 24th, and you can check that at this list of IRS forms and dates. IRS Forms Available Estimates