Need advice - Best course of action

I need advice on the next step to take with a collection item on my credit report. My ex-husband went to the dentist while we were married so his bill had my name on it too (the services were in 2002, the bill went to collections in 2004 - we divorced in 2003).

In any case, the debt with the collection agency showed up on my credit report (I noticed in early 2007) and I disputed with all 3 and all 3 agencies "verfied", so then I went to the collection agency and they sent me to the dentist. I talked to the dentist office and explained this wasnt mine, they pulled up the bill saw his name on it and said they would stop reporting. They told me the quickest way to get it removed would be to dispute with the agencies again and it should come off in less than a month. They also gave me the bill with my ex-husband's name on it.

So I did what they suggested and TransUnion and Equifax deleted the account. Experian sent me a generic letter saying they already investigated and will not re-investigate. I have written them 3 more times and sent copies of the dental bill. The debt still appears on my report and even my letters to the collection agency come back to me "not at this address" - I think they are closed. I sent the returned mail to Experian as well with a letter sayign the collection agency doesn't exist anymore. Yet Experian won't look into it, they "verified" this debt over a year ago so they are just leaving this on my report. I have called and they told me to mail in the bill, I did, got the generic "we previously verified so we won't look into it again" letter back, I try to dispute online, it won't let me says "previous dispute verfied". My credit report with Experian does say in the comments "account disputed by consumer" but they wont' take it off or even look into it.

Is there a management office for Experian, or some other place to contact that won't give me the same robot answers and will actually look into this so this can be removed. It's $197 and some people have told me to just pay it, but that seems silly when the dentist office doesn't even want the $ from me and I don't think that would even satisfy Experian, I have proof the debt isn't mine and they won't look at it.

What is the next step?