Why is it taking so long to drop my employer coverage?

Why can't I just tell my employer that I don't want insurance coverage through them anymore? I have already obtained coverage through my husband's company and all I want to do is drop my coverage through my job. I've been trying to do this for over a month now and it has cost me over $400 so far while they keep wanting more and more paperwork from me. They are trying to make me prove coverage through my husband and I've shown them approval letters and my new insurance card which has both of our names on the front. Is what they're doing to me legal? It's my money and my choice right? If it wasn't being deducted from my paycheck, I'd just quit paying and they would drop me in a heartbeat, but I don't have that choice.