The huge shake-up in directory enquiries services has got off to a smooth start, according to the telecoms regulator Oftel.
BT's 192 service is being replaced by more than 20 alternatives
BT's directory enquiry services, 192 and 153, stopped giving out telephone numbers after 46 years on Saturday night.
People calling those numbers now hear a recorded message with a freephone number that selects at random one of the more than 20 replacement services, which all begin with 118.
A spokesperson for Oftel, which is behind the change, said: "The changeover happened as planned and everything has gone fine since.
"Our project manager has been in contact with all the new providers and everything seems to be going to plan so far.
"But until we see the statistics, we can't be sure how many people have been mis-dialling."
A spokesman for 118 119 said his firm was "coping very well" with a 20-fold increase in calls since the changeover, but he was critical of the way Oftel had managed it.
He said: "I was surprised that Oftel did not choose a gradual, smooth switch over, allowing the new call centres to gradually develop the necessary experience."
Oftel has said the overhaul will mean improved value for the £300m callers spend on some 700 million calls to the service every year.
There is a vast difference in what callers pay depending on what number they ring and the Consumers' Association is urging Oftel to inform callers about the different tariffs.
While one of BT's competitors is offering nearly a million registered customers free directory inquiry calls, a leading mobile phone company is charging up to £2.50 a minute.
The Number's runners are looking for quirky cult status
Consumers' Association senior researcher Jenni Conti said: "Consumers are likely to be bamboozled by choice."
New companies have spent millions of pounds on marketing campaigns.
Reports suggest Britain's directory enquiries market, the largest in Europe, could be worth up to £1.3bn within three years.
And as companies jostle for their share of the pie, research suggests BT's own 118 offering is falling lower on callers' radar screen.
Among the major spenders in the 118 branding war have been The Number, Conduit and BT.
The Number, owned by the US call centre group InfoNXX, has very noisily sought to create a distinctive brand, with its two moustached 118 runners campaign on television, billboards, ice-cream vans throughout the UK and a T-shirt campaign through the Cancer Research charity.
"Number memorability is the key thing," The Number's marketing director Alex Harris told BBC News Online.
Ms Harris said the comic campaign is making a potentially uninteresting product a saleable commodity.
"It's a fairly dull industry, which we wanted to spice up with an engaging, fun vehicle."
BT is responding by spending its £10m marketing budget on reinforcing a 'tried and tested' brand.
BT also offers a free directory enquiries service on its website.