Martin Brown wrote:

Andy Burns wrote:

Chris Holmes wrote:
it's just a normal London number, charged like any other 01/02/03
call.

Not sure about that. Some sources say it is a local rate number.
(although they are London based organisations saying it)

For business lines there's no per minute difference between
local/national or day/evening/weekend calls any more, just geographic
01/02 and non-geographic 03 calls all charged at a single rate 24x7

But for residential lines there's still a difference between
local/national, day/evening/weekend rates, so that Teams number could
potentially be cheaper for some customers than others if they're in
London, but it won't be premium for anyone.

For chapter and verse see "the" price list, inland call charges subparts
1 and 2, obviously non BT/openreach suppliers may vary

http://bt.co.uk/pricing/current/Call_Charges_boo/0016_d0e1.htm#0016-d0e1

Worth reminding that there are various nasty price exceptions to look
out for within 00/05/07/08/09 ranges ...