我杯具了

昨天偶然发现我的credit 从将近八百降到七百以下，due to a collection agent's report of an unpaid medical bill. Called the hospital and insurance. Insurance told me ALL were paid. 正在与collection agency交涉中，刚留言给他们。
有经验的同学请指点。
Can I demand them delete it immediately?
How likely would I win if they refuse and I sue them?
谢谢！