How to leave company halo 5
This topic should get you all sorted: https://www.halowaypoint.com/en-us/forums/8f4648981f554a9d86527a5754966e89/topics/how-do-you-leave-a-spartan-company/c99744af-21b9-4e71-9a78-36718b2fde7b/posts.
If you still need further assistance, maybe post a comment in there 
Happy Haloing!