BT is to charge more for its 118 500 directory enquiries service, the telecoms giant has confirmed.
The new 118 services have been heavily criticised.
Customers wanting to use the service will see initial charges rising from 25p to 40p from next month.
However, the subsequent per-minute cost will fall from 30p to 15p, including calls put through to requested numbers.
BT, which claims a 40% share of the UK enquiries market, said the price rises were in response to the growing numbers of people using call connect.
"Customer habits have changed due to the availability of call connect and classified searches," said Paul Elliott, chief executive for BT Directories.
"The average call is now close to one minute, rather than the 30 seconds that was typical for calls made to the old 192 number."
Directory enquiry services have suffered a barrage of criticism since they were deregulated in August.
With callers now free to choose between 20 rival directory enquiries firms - all with different numbers, starting with 118 - some consumers have complained that the new system is confusing.
And while BT Group claims its new pricing structure will provide a more economical service for its customers, rivals in the 118 marketplace are not so sure.
Share Communications, the company behind 118 499, claims BT's new charges could cost 11% more on the average 40 second call to directory enquiries.
"This represents four times the rate of inflation," said Steve Warner, managing director of Share Communications.
Changes to call connection charges, Mr Warner claimed, would only benefit around 10% of callers of 118 500, while 90% of customers would be left with a higher bill.