If you're bouncing back & forth between part-time inside work at a low wage, and "full-time" cover driver at a higher wage, this is probably the result. Dues should be based on your wage rate, but which one? Maybe your local has a lesser or no initiation fee for part-time, and you've now worked enough "full-time" cover driving to be required to pay a full-time initiation fee. When you call the union office, are you talking to someone specifically in the dues department? Forget the stewards/agents/reps on this, it's not their forte. What's your local? 773? Did you talk to or better yet, email Lisa? Maybe try the meeting sunday.