Specialist mentoring from NAS- information sought

My DSA allowance allocated me help from NAS for study mentoring, but I am not yet able to access it. I am on study leave but have an assignment to complete which I am having real problems with and I am not allowed help from student services at university because I am on study leave. Would I be able to access one-off help from NAS to allow me to complete the work? Can anyone in receipt of such mentoring tell me if advisers can guide mentees on specific assignments if they have been designated for credit? Thanks in advance