The Prime Minister, or rather the DoH official who drafted the petition reply for him, was talking rubbish. This was simply falsely justified buck-passing.
Telephone tariffs are not set locally. Furthermore, the principle of the NHS being "free at the point of need" is too politically sensitive to be at the discretion of unaccountable local Trusts. (Even those granted "foundation" status seek to recruit their own "members", to whom they have a very limited accountability.)
Ofcom has made a complete mess of regulating use of NGNs in general and fell out with the Cabinet Office over implementation of 03. Now that 03 is in place, all that Ofcom can do is to encourage its use. It could certainly be more vigorous in this activity, but does not hold powers to compel anyone to adopt 03 or to abandon revenue sharing numbers.
Government departments and other public bodies must each make their own decisions, although the Cabinet Office, through the Contact Council in particular, has a crucial role to play in helping these to be made correctly.
Those who despair of civil servants can only turn their attention to the relevant Ministers and Select Committees of Parliament at a UK level, and their democratically-accountable equivalents locally. If we despair of both groups, then we have no hope of achieving anything and become moaners rather than campaigners.
There are modest successes to report. Ofcom has regulated for 03 and both civil servants and elected politicians have been seen to decide to adopt it in place of 08xx numbers. It is happening very slowly, as anyone with experience would expect, but it is happening.