This should cover 23 hours on weekdays during the summer and 24 hours on weekdays during the winter.
UK: 07:30-20:00 Local +44 191 490 7901
US: 07:30-20:00 Eastern +1 800 452 1201
HK: 09:00-17:30 Local +852 3002 1208 (weekdays only)
Otherwise there's coverage between 07:30 - 01:00 GMT (Adjust for DST when applicable) by using US and UK numbers.