BT is to start charging for its 1471 call return service from 1 August.
BT is facing tough competition
Customers will pay 6p when they use the 1471 service to return a call. However, just dialling to obtain the number of the last caller will still be free.
The cost of calls to the speaking clock will double to 20p and the BT Ring Back service will cost 15p, up from 10p.
In addition, the monthly rental charge for Enhanced BT Answer 1571, the personalised messaging service, will increase from £1 to £1.50.
BT has 19 million customers and supplies telephone services to 70% of UK homes.
The company is fighting hard to hold on to its dominant position within the UK residential phone market.
In March, BT announced that it planned to move nine million existing BT standard rate customers to a new tariff, meaning higher line rental in return for cheap calls.