UK businesses seem to be connecting with the phone code changes on 22 April, when area codes and local numbers for six UK areas, including London, will change.

Many of the systems used by UK businesses are affected, including call barring, alternative network routing, private payphones, ISDN and call management systems. Telecoms watchdog Oftel has recommended that companies address these issues well in time.

Calling line identity, routers connecting Lans and stored numbers, both local and national, alternative network routing and international ISDN should also be upgraded to avoid missed or mis-directed calls.

Users contacted last week said their arrangements were well under control. Woolworths is nearing completion of reprogramming or updating of all of its telecommunications systems. A spokesman for the company said preparing for the number changes has been more "a nuisance factor" than a major cost issue. "It's how to communicate the numbers that causes the real trouble," he said.

HSBC bank is in the process of informing its customers of the changes, but expects the cost to remain relatively low. "It's been dealt with and is under control. It's only been a change and check in systems, so not a mega cost, not as bad as when the (0181) numbers were introduced," said a spokesman.

Karen Millen, the high-street fashion chain, is putting in a bank of new telephones and has incorporated the price of system upgrades into the refurbishment costs. Guy Weller, head of IT at Karen Millen, said the retailer is effectively doing it from scratch and will not be concerned in April. "We may have the odd problem with fax machines - but it is certainly not going to be business critical."

The so-called Big Number is the most complex set of changes ever made to the UK's numbering system. Oftel says the changes are necessary because demand for phone lines in homes and businesses have rapidly increased because of the internet and ecommerce. It estimates that demand for new numbers could reach six million per year for the next 15 years.

The six areas impacted are Cardiff, Coventry, London, Portsmouth, Southampton and Northern Ireland.