I have been asked to reply.
The Government recognise that the issue of fair and easy access to public services is a very important one, and the Cabinet Office has already worked with Ofcom to establish the 0300 telephone number range which offers a fairer tariff regardless of the line from which citizens call (including mobiles).
The Cabinet Office, through the Contact Council, is currently conducting a comprehensive survey of the different number types, such as 0845, 0870 or 0800, used by central Government Departments and agencies, including consideration of their mobile telephone access. The Council intends to use the results of its survey to steer a future cross-Government approach to the use of phone numbers that ensures fair and easy access to public services for all, especially the most vulnerable and disadvantaged. Officials leading this work are already engaging with mobile telephone providers. A meeting with Ministers may be appropriate once the Council's research is complete.