If they are not, you need to amend this in the students profile on the extended tab, under the Service Child Information section and set them to 'No'.
Also check their profile for eligibility for free school meals. If they are a service child they are not eligible for Free School Meals.
This can be updated on the extended tab of the student profile under the Further Information section.
This is what the DfE says:
Confirmation is not acceptable. As this impacts on pupil premium funding a reason must be provided why a pupil is both FSM and a service child. Please note the pupil must 'live' with the parent who is in the services to be recorded as a service child.