Does any one know who a person would call to have a Tax Lien from their ex-husband taken off their personal credit report?

I'm trying to help my older sister get her credit report straighten out and that cheating ex of hers has went and messed my sisters life up again with all the IRS Taxes he still owes from when he had his own business.... and my sister is suffering as they keep posting this darn Tax Lien on her SS # when it should only be on his number.

Please... Don't suggest we contact the IRS as we have been there done that and it has not helped.

Any advice would be appreciated..... Thx.