Can one appearing Manager of Bank represent all other Branch

In a Defamation suit against the Bank, defendant no. 3, a manager of a branch of the Bank appeared and filed a WS. Ex parte was declared against the defendant nos. 1, 2, 4 to 7. Is there any judgement which states that all the defendants are the same entity and filing of WS by one can be constructed as the WS being filed by all the Bank branches and officers ? If so, be gracious enough to provide the citation.