Quoting of Helsinki Telephone's E shares commenced on the main list of the Helsinki Exchanges on 25 November 1997. In June 1998, Helsinki Telephone Association changed its legal form to that of a cooperative. Upon the transformation, the Cooperative sold 4,000,000 Helsinki Telephone E shares previously held by it to international institutional investors. At the same time, Helsinki Telephone issued 4,000,000 new Helsinki Telephone E shares.

By the end of February 1998, the Cooperative had converted all 27,295,400 Helsinki Telephone K shares in its possession into E shares. After the conversions, and the private placings to Oulun Puhelin Oy and OKO Bank, the Cooperative's votes as a shareholder of Helsinki Telephone fell from 91.1 per cent to 68.4 per cent.

As at 31 March 1999, the Cooperative had approximately 348,000 registered members. In 1995, the number of Membership Certificates was capped at 575,000, and the issuing of new Membership Certificates ceased in January 1998. From 19 October 1998 throughout 4 May 1999, Membership Certificates were listed for trading on the pre-list of the Helsinki Exchanges. On 11 May  1999, the Cooperative transformed into HPY Holding, and the members registered in the Cooperative's register of members became the shareholders of HPY Holding. One Membership Certificate entitled the holder to 150 HPY Holding A shares, the trading of which commenced on the main list of the Helsinki Exchanges on 1 July 1999.

HPY Holding Corporation and Helsinki Telephone Corporation merged on 1 July 2000. The merger of HPY Holding Corporation and Helsinki Telephone Corporation was the final stage in the transformation process which had started in 1994. The purpose of the restructuring was to build a leading edge and customer-oriented company that creates shareholder value. In the merger, Helsinki Telephone’s business operations were transferred to HPY Holding Corporation. Upon the merger, HPY Holding Corporation adopted a new corporate name: Elisa Communications Corporation. Pursuant to the merger plan, shareholders of Helsinki Telephone received as merger consideration 2.16204 HPY Holding A shares for each Helsinki Telephone E share. In the same connection, the shares of Helsinki Telephone were declared null and void, and HPY Holding A shares were converted into A shares of Elisa Communications. Trading of Elisa Communications A shares commenced on the Helsinki Exchanges on 3 July 2000.

The purchase prices of Helsinki Telephone Association's Membership Certificate since 1996