How can I untangle this hair?

Ok well I bought a life size doll Rosy (Smoby is the company here is a link to the doll I bought a href="http://www.argos.co.uk/static/Product/partNumber/3520594/Trail/searchtext%3EROSY+DOLL.htm" rel="nofollow"http://www.argos.co.uk/static/Product/pa…/a ) And Rosy has long hair it is knotted and matted badly and I can't style her hair...... I have tried shampoo and conditioner and brushing it to untangle but nothing will untangle her hair have you got any ideas on how to make the hair nice and smooth like it was when i bought her please??