I am a bit confused about being banned from a practice

[Gruntster]

Could someone explain this to me? I got in line to cap a practice last night and when my turn finally came up I claimed the frequency and jumped in. A minute or so later Pez jumps on my frequency and somehow takes over the freq as captain and .bans me from the freq booting me to spec? Apparently there is something my noob ass is unaware of as far has how that shit works.