THOUSANDS of Hampshire businesses will have to pick up a massive bill when millions of telephone numbers change today.

Southampton and Portsmouth area codes - currently 01703 and 01705 respectively - will both change to 023.

And local telephone numbers in both areas will increase from six to eight digits, with Southampton numbers being prefixed by 80 and Portsmouth by 92.

However, until next April, these new eight-digit numbers will not work unless used with the new area code - even when making local calls. There are fears the changeover - the third in less than 10 years - could prove even more chaotic than Phone Day in 1995.

That only involved inserting a one after the zero in national area codes.

This time the changes are much more complicated as there will be different prefixes to add to local numbers as well as changes to area codes.

The omens are not good. Callers to the Big Number helpline at the weekend were told: "Sorry, there is a fault. Please try later."

And on the eve of the big shake-up the helpline, set up by the telephone companies, was unmanned because it was a bank holiday.

A spokesman for Southampton Chamber of Commerce said business was bound to suffer because of confusion over the new system.

He said: "While one can appreciate that the demand for new numbers is growing all the time, it seems ridicu-lous to put people through all this so soon after the last one.

"This is going to hit all sorts of businesses, large and small, and then there is the lost revenue to consider due to public ignorance of the changes.

"Not enough has been done to prepare people for what is quite a complex set of changes." Telecommunications watchdog Oftel said the procedure was vital to keep up with the growing need for new telephone numbers.

More than ten million telephone numbers will change in all, including those in Cardiff, Coventry, greater London, and Northern Ireland.

Current local numbers, like the Daily Echo on 424777, can be used until April 2000. From then new local numbers come into operation and people will have to add the new prefix to make it 80424777.

Current STD codes - for example the Southampton code 01703 - will still work until autumn 2000 to give people time to adjust. After autumn 2000 people will have to use the new code 023 for Southampton.

A spokesman for BT said: "There's no way I can justify the changes because they're not our changes. "This is a decision by Oftel and we are having to implement it.

"The change in 1995 also happened when Oftel took control of the numbers. They know the big picture, the new companies, the competition and the increased demand for numbers.

"We accept that we need more numbers and that allocating new numbers is so much more complicated now."

The other significant changes include inner and outer London codes - currently 0171 and 0181 respectively - which will be 0207 and 0208. Mobiles and pager numbers nationally will begin 07.

Converted for the new archive on 25 January 2001. Some images and formatting may have been lost in the conversion.