Changed Domain for site – with webhost – now site not working

I have a site that is @ yrs old – which was olddomain.com/subdir and now i requested from host to change it to newdomain.com – however they changed it to newdomain.com/subdir – now whan i goto site newdomain.com it forwards to newdomain.com/subdir automatically – also i have lost all my posts and links and only have front page that looks the same.. all links are broken and 404 error – i cannot login to backend either.. Some help with this would be greatly appreciated.. The host said they would do this for me but now wont finish it and said they could revert it back to olddomain/subdir – Please help.. Thx in advance