Our union guys were pretty good about telling us who to call first.
If we had a scheduling issue, call the scheduling chairman before contacting the company. 1) That saves a pilot making themselves look like an idiot because they didn't understand the CBA, and 2) It would also save a pilot from having to directly communicate with a company representative if there was an issue. The issue, whatever it was, would be handled immediately by our scheduling chairman. He'd get a decision, and then the pilot would be contacted by him and a company representative telling him the end outcome.
Kept the peace, and kept the company and pilots in check.