Rain Guard Water Sealers VG-7001 VandlGuard Non-Sacrificial Anti-Graffiti Coatings READY TO USE covers up to 300 sq. on painted and unpainted surfaces. 1 Gallon

Two ways you can deter the marker is to either have the call box polished crazy smooth or apply an anti-graffiti coating. Even permanent marker will easily smudge and smear - and wipe off quickly. Example: https://www.amazon.com/International-VG-7001-Vandlguard-Non-Sacrificial-Anti-Graffiti/dp/B00AL3S8Z0