First, why would they drop Part A... there's no cost and I recommend that any of my clients, turning 65 and still working, enroll in Part A. Once you're enrolled in A, theres no reason to drop it. They can disneroll from Part B by filing a FORM CMS 1763.
THen, when they decide to retire, or lose coverage they will need to reapply for Part B (and showing proof of continuous coverage during the time they were disenrolled). Ive found that once they are re-enrolled and eligible for Part B that does trigger a GI period. I;ve not had any issues with my clients that have done something like this in terms of getting any coverage they want.
