[tracker2] blocking a call sign from i-gate

[Ron K7CDL]

i have one person that does nothing but hammer the system and has been tould 
about it sience last year and still no fix. how do i block a call sign to not 
allow them into the system? is there anyway to block them out of the tracker so 
it doesnt digi and it doesnt even allow it into the KISS mode?
Ron