I don't think I've ever seen someone so opposed to potential for promotion... You do know that promotions are a GOOD thing right?....
Bottom line is, you bust your ass you get paid well. Stop complaining about having to have a little bit of "extra responsibility" (which is a joke as far as GSA goes) and suck it up, do the work, earn your promotion. Or just frig off, tell your ETL you NEVER want to go anywhere in your job/life and continue biding your time as a cashier. Wont make any difference to them, they'll just find someone else with some drive and motivation to do it.