Is commission the new layoff?

Last November I applied for the position of marketing director for a company that manufactures reusable and disposable thermometers (don't judge - times are hard). It's a small local company that has huge potential. Long story short, they hired someone else for the job, but felt my computer skills were invaluable and hired me to work from home doing research to support their sales staff (SWEET). Fast forward 5 months - turns out they don't have a sales staff and somewhere along the way, I wound up using my own research to make sales calls and send literature to prospective clients. Well, last month, they called me in for our "monthly meeting" and I was informed that I would be moving towards a commission based compensation. What the heck!? I didn't even ask to do sales, why am I being punished for something I didn't sign up for? Needless to say, this is not going to work for me. I cannot possibly be expected to work for free. Oh well...