Not sure I understand what you mean here, can you be more specific? Generally speaking, channels do not "belong" to a user, every channel within a given Team can be accessed by all team members, and is "owned" by all team owners. Private channels have their separate membership/ownership, but are still associated with the "parent" Team, so again unclear if that's what you are looking for. Are you perhaps looking for a list of all Teams (and private channels) a given user is a member of?
And since it seems that you are looking for information on the corresponding Graph API endpoints, I'll adjust the question tags.