HONGKONG Telecom has opened a representative office in Shanghai to upgrade its services in the mainland. The company, working with Shanghai's telecommunications authority, will upgrade telephone network operation capabilities in the mainland through technology transfer and professional training. ''Shanghai is expanding rapidly to become China's major financial centre. Modern telecommunications facilities are an essential element in this process,'' said Hongkong Telecom chief executive Linus Cheung Wing-lam at the opening of the Shanghai office yesterday. He said technical professionals and management expertise were important to secure rapid and steady progress in the development of the industry. Hongkong Telecom had achieved this and hoped to share its experience and contribute to the building of a new Shanghai, Mr Cheung said. Hongkong Telecom and Shanghai Posts and Telecommunications Administration (SPT) have been involved in several joint projects, including international private leased lines, roaming for mobile phone customers, radio paging and long-distance calling card services. SPT deputy director Cheng Xiyuan said: ''The development of telecommunications is one of the major factors contributing to the economic success of Shanghai.'' Shanghai has in recent years seen rapid growth in its posts and telecommunications operations. Last year, total volume of both traffic and income grew by more than 50 per cent compared with 1992. Communications traffic between Hong Kong and China accounts for 50 per cent of Hongkong Telecom's direct international calls.