The work you describe may be considered self-employment income by the IRS. The things that make is so is the regularity of the work and the fact that you are providing services for compensation. If that is so, then the income is being correctly reported on the form 1099-NEC. The provider of the form is the only one who can change it.
It may help to read this article from the social security administration, which indicates that volunteer firefighters are normally considered employees, which is simlar to being self-employed: Tax status of volunteer firefighters
Here is a quote from the article: