1099-NEC Former Employer

I received a 1099-NEC from a former employer for commissions due after termination. I was employed with another company full time while receiving this compensation. I'm not self employed and don't have a business yet TurboTax is still making me file a Schedule C and name my business for this income. I also get hit with self-employment taxes although I'm not self-employed. How do I fix this situation?