TWO of the territory's top companies claim the Government has short-changed them over the release of the new one-dollar coins. Hongkong Telecom says the Bauhinia coins are still not accepted even by modified payphones and Swire Bottlers say their vending machines also can't cope with them. Both companies say the coins, released last October, are different to the original prototypes circulated by the Government. Both spent time and money modifying their equipment to bring it into line with the prototype specifications - modifications that have now proved useless. But yesterday a government spokesman denied the coins were different to the prototypes, adding the general-circulation coins were made to the original specifications, with only minimal differences possible. Now both Telecom and Swire are considering their next moves - including a possible approach to the Government for costs - while they repeat expensive remodification programmes. Hongkong Telecom said in an official statement the ''error'' had caused an eight-month delay to the modification process causing grave inconvenience to its customers. A spokesperson for Swire Bottlers said its modification programme for 5,000 beverage vending machines across the territory, which had just been completed, would now be repeated because of the foul-up. ''We have around 5,000 machines in Hong Kong and we managed to have them all ready on time for the release of the new coin last October,'' the spokesman said. ''But when we received the coins we were rather shocked to find that they didn't even fit the machine properly.'' Telecom's announcement was in the same vein: ''Due to discrepancies between the sample coins on which our 6,000 payphones were based, and the coins eventually put into circulation, some of the new coins are not accepted by modified payphones.'' But Roger Candler, head of supporting services for the Hong Kong Monetary Authority, said the circulated coins were made to the same specifications as the samples adding the only possible error could be in the way the coins were plated. ''These problems were not expected. I'm not specifically sure where the source of the problem lies but I doubt it has anything to do with the specifications originally set out. In terms of size, weight and diameter, etc, the coins are exactly the same asthe samples given,'' he said. ''The only cause I can possibly see would have to be in the plating process. Plating can cause minute changes to the coins - to thickness - but these differences are so small it shouldn't make any difference. Perhaps coin-operated machines nowadays are too sensitive and sophisticated.'' When a coin is dropped into a vending machine slot it travels down a small shaft to a catching device that only allows coins of a certain shape and weight to pass through to the money bag. If the coin is accepted the machine will operate and if not, the coin will be rejected. Spokesmen associated with the companies said expenses were twice original estimates because of the problem and the resulting re-modifications. ''As for sensitivity of the machines, they are tuned in such a way to allow for flexibility in accepting minutely different coins. Not to do so would be ridiculous because many coins are old and slightly eroded. There has to be some give and take or elsethere would be virtually no coins accepted at all,'' said one spokesman. The companies say they are now concerned about the planned introduction of the new $10 coin in the next few months.