If you are not happy with the response you get you are entitled to a review in the first instance. Write to:-
FOI Reviewer
NHS Lanarkshire Headquarters
Kirklands
Fallside Road
Bothwell
G71 8BB
If you are still unhappy with the response after the review you can then appeal to the Office of the Scottish Information Commissioner. This is explained on the Commissioner’s website – http://www.itspublicknowledge.info/YourRights/UnhappyWithResponse.aspx