My daughter was hospitalized. Hospital asked if I had extended health benefits. I said yes for semi private room. This week I received notice that my benefit company had denied claim for 1000 as I didn't have coverage for semi private. I looked in benefit booklet and it said I did. So I phoned them and they said as of April 2010 the employer had taken the semi private hospital coverage away. I don't remember getting any notice of this and was not aware. In 2009 I had surgery and had semi private coverage. Should my employer not have told us of this change and are they responsible now to pay my bill

Sure you should have been informed of the change but check with your HR department to see how they did that first. I'd talk back to the hospital about why they did not confirm your health plan benefits and just took your words for it. Folks often misunderstand their plan so hospitals routinely, except yours, call and confirm.

The insurance company sends you all sorts of info, any time there are changes, I would be sure you got a notice, hidden and tucked away in small print in the pages of you get from them.

But the place where you work merely provides the ability for you to get the insurance, any agreement or contract is between you and where you work ( unless this is insurance funished by your union)
But no they are not responsible,

I called hospital and because she was in for pyschiatric reasons they decided to foot the bill. I would never have known if I hadn't tried. 1000$ saved