PostBank was the trading name of the Post Office Bank Limited, a bank

Bank

A bank is a financial institution that serves as a financial intermediary. The term "bank" may refer to one of several related types of entities:...

 owned by the New Zealand Government. PostBank was formed when the New Zealand Post Office

New Zealand Post Office

The New Zealand Post Office was a New Zealand government department.As a Government Department, the New Zealand Post Office or N.Z.P.O., previously the Post and Telegraph Department or P & T, had as the political head the Postmaster General who was a member of Cabinet, and, when it was a separate...

 (a former Government Department) was split up by the Postal Services Act 1987 into Post Office Bank Ltd (trading as PostBank), New Zealand Post Ltd

New Zealand Post

New Zealand Post, commonly referred by its acronym, NZPost is a State owned enterprise responsible for providing postal service in New Zealand.-History:...

  (a Postal Services company) and Telecom Corporation of New Zealand Ltd

Telecom New Zealand

Telecom New Zealand is a New Zealand-wide communications service provider , providing fixed line telephone services, a mobile network, an internet service provider , a major ICT provider to NZ businesses , and a wholesale network infrastructure provider to other NZ CSPs...

 (a telecommunications company). It purchased the assets of the former Post Office Savings Bank.

PostBank was sold two years later to ANZ http://www.anz.com/australia/aboutanz/corporateinformation/historyofanz/default.asp, with the PostBank brand being absorbed and finally removed by the late 90's.