GetListItems Method + ViewFields parameter not getting overridden + sharepoint

I want to get the data for all the fields and rows from a sharepoint list. So, i gave all the fields in the viewFields parameter in the GetListItems() method specifying like below:

<ViewFields>
   <FieldRef Name="ID" />
   <FieldRef Name="Title" />....
</ViewFields>

But the fields are not overidding the fields given in the default view ie. i am getting data only for fields shown in the default view and not the fields i am giving in 'ViewFields'. Why is this happening? According to the doc:

http://msdn.microsoft.com/en-us/library/dd586530%28v=office.11%29.aspx

It should override the fields. My main aim is to get the data for all the fields and rows.So if any other work-around exists, please let me know. thanks.