About 300 airport railway workers are to complain to the Mass Transit Railway Corporation about a contractor they say owes them $15 million in overtime payments. Talks between the workers, mostly electricians, and the construction company, Balfour Beatty, collapsed yesterday after its offer of $25 for each working day from January 1 was rejected. Workers' representative Chung Kim-shun said staff felt they had been cheated by the employer, who 'had altered the employment contract to make it a nine-hour working day instead of eight'. 'Some of the workers are holding three copies of the contract and they are all different in details,' said Mr Chung. The contractor was unavailable for comment last night.