I was a CWA member for over 20 years. Not by choice, I had to join within 30 days of starting work or leave.
Seniority rules in unions. No matter how hard you work, how good you are, you get nothing, go nowhere, without seniority.
Over time, it becomes a "good old boy" system between the union and management. Seniority is gradually replaced by the "who you are" and "who you know" system.
If you think you're having problems getting paid, chargebacks, travel, etc. It could get worse after a few years once the "boys" sit down and figure out how to screw you over even more!
And you will pay them every month [union dues] for the privilege!