FOR once the powers that be have sided with the little guy. Hongkong Telecom has been told it can no longer force customers to pay a premium for hooking fax machines to telephone lines. Better still, it has been advised to let them know about the change. Usually when a company the size of Hongkong Telecom charges the customer for providing no obvious extra service, the consumer has little comeback. But this time the 177,000 subscribers who have generously paid Hongkong Telecom an extra $150 million over the past three years have found a champion in the Government-appointed regulator, the Office of the Telecommunications Authority. If it is well-managed, Hongkong Telecom should welcome OFTA's interference. A little competition concentrates the management mind and leads to improvements in efficiency and customer service. In the absence of any competition, OFTA should prove to be a useful reminder to the phone company that it exists to serve the customer as well as to make huge profits for its shareholders.