Your number's up, telephone campaigner warns.
The old 0203 code and numbers are switched off on August 19.
And they should update 'hidden numbers' stored out of sight and out of mind in equipment such as fax machines, computers and switchboards, The Big Number campaign warned yesterday.
Coventry numbers changed on April 22, with a new (024) area code and 76 added to the front of local numbers. A 'safety net' specified by telecoms regulator Oftel means that voice and data calls have continued to get through using the old (01203) code and numbers.
But the net is switched off on August 19 as the final stage of a three-year programme. After this date, voice and data calls using the old code and old numbers - within Coventry or into Coventry - will fail.
Voice calls using the old code and number will go through to announcements. Data calls such as faxed will not recognise these announcements and will continue to misdial.
Network statistics show that 75 per cent of calls connecting to Coventry numbers in July were made using the new (024) code and numbers. A quarter still use the old (01203) code and number.
Andrew Lawford, campaign manager for The Big Number, said: 'We suspect that many of the calls made with the old code are using stored numbers, for example the memory facility in fax machines.
'Businesses dialling into Coventry may not have thought to make the necessary changes, because these numbers tend to be hidden out of sight and out of mind. Our latest research shows that three in five UK businesses have not finished changing numbers stored in faxes, switchboards, databases and other equipment.
'We strongly urge Coventry businesses to warn their contacts in the West Midlands and beyond that they must use the new (024) code and eight-digit number when calling Coventry from August 19.'
Information is available on www.numberchange.org or by calling free on 0808 22 4 2000.