Work Accommodations

Hello, I’m a full-time employee for a very large company. I have become permanently disabled 2 years ago and have had medical accommodations for reduced work hours and other job functions. My store manager has brought up me switching to a part-time employee due to my reduced hours, however, that will change my medical benefits/deductables/ etc. so I’d prefer to stay the way it’s been. I’ve been told they cannot make me switch, unless it causes financial hardship to the company, which it does not. Like i said, it’s a very large company. Am I correct that hey cannot force me to change? I’m in NY also. Thank you.