Millennium bug busters have warned revellers not to make unnecessary phone calls during the rollover for fear of crashing systems, even if they are Y2K compliant. And people worried about their savings have been assured that bankers will update and store account records before the clock ticks to the zero hour tomorrow. Wrapping up the Government's $524 million rectification works for its key computer systems, officials were 'cautiously optimistic' of having a smooth rollover. 'I think on the whole, we have done pretty well,' said the Deputy Secretary for Information Technology and Broadcasting, Jessie Ting Yip Yin-mei. Mrs Ting will head a Central Co-ordinating Centre from noon tomorrow to monitor compliance until 8pm on January 3. The overseas situation will also be monitored. An additional 13,000 civil servants will be on duty during the holidays, with another 10,000 on stand-by. Tests on key government systems will be carried out on January 1. Mrs Ting also mapped out a list of dos and don'ts to minimise chaos. It included avoiding ringing up friends or relatives at midnight for fear of overloading the network. 'If you're thinking of saying 'hello' to your friends the minute the clock rolls over to 2000, maybe you can wait a few minutes. 'This is purely a question of system overload, nothing to do with the Y2K,' she said. The readiness of small and medium-sized enterprises appeared to be less certain. Mrs Ting said companies were aware of the problem, but she did not say if they were fully compliant.