header details not changing with body in a groupp report

Dear Expect;

A <B>grouping report</B> in <B>.rdlc</B> has this  issue, as the body details changes on each page or pages for the other groups as the listing roll out , the corresponding header details don't appear, the header details are those  of the initial group.


What it means is that while the body details changes to reflect the various listing, the 

header details are those of the first group.



How do I correct this problem ?

Thanks