Submitting a VA Complaint Outside of the Local VA.

I was rejected from a scheduled VA procedure by a nurse on an administrative technicality unrelated to my condition, after scheduling a 100 mile round trip with my Medicare transportation provider. This is disgraceful and unprofessional, especially since I initially rescheduled the appointment in order to comply with the requirement to not come unaccompanied. The Patient Advocate Office states that they can only file my concerns with the same department that I am complaining about, which seems nonproductive and disingenuous. How do I file a complaint outside of the local VA department?