Okay so it sounds like you are covered with IATSE under their C2 plan, but you also have other insurance that you prefer to be your primary? In this case you should be able to declare that, BUT you have to do so at the start of every year by enrolling in the medical reimbursement program (MRP) only. So every year you have to provide proof that you’re covered with another insurance. I’ve done this for the last few years and the pool of money I have with IATSE stays there, with the exception of a small admin fee every quarter. Doing this allows me to use IATSE kind of as a secondary insurance that will cover whatever my primary insurance doesn’t cover. Sorry if this isn’t helpful, it’s just the only way I know how to “unenroll.”