Since 2009, 0845 and 0870 numbers are usable within "inclusive minutes" in BT packages. Ofcom removed revenue sharing from 0870 and made 0870 inclusive in 2009. BT expected Ofcom to remove revenue sharing from 0845 too. BT made 0845 inclusive but Ofcom didn't proceed with the expected changes. BT subsidises calls to 0845 numbers.
It's 0843, 0844, 0871 and 0872 numbers that are the expensive ones from landlines. These are revenue share numbers. In comparison, most people can ring 01 and 02 numbers for up to one hour at no cost since call packages were introduced in the early 2000s.
All 084 and 087 numbers are expensive from mobiles.
Whenever you see an 084 or 087 number advertised, replace the 08 with 03 (keeping the rest of the digits the same as before) and see what you get. It will either be answered by the correct company or will lead to a "number not yet in service" error message.
03 numbers were introduced in 2007. These are usable in inclusive minutes from landlines and, crucually, from mobiles too.
03 numbers cost the same as 01 and 02 numbers if you have to pay for them (i.e. from pay as you go mobiles and from landlines without inclusive minutes).
034 and 037 numbers are already reserved for the users of the matching 084 and 087 numbers.
New users can choose 033 numbers, and certain organisations can use 030 numbers.
Ofcom propose cleaning up the 084 and 087 number ranges. In 2013, several changes are expected:
- 0870 will return to revenue share and align with 0871 and 0872 revenue sharing numbers.
- 0845 and 0870 will no longer be inclusive calls from landlines.
- 0845 will align with 0844 and 0843 revenue sharing numbers.
- The Consumer Rights Directive will force many 084 and 087 users to move customer service and other similar functions to 03 numbers. This will benefit landline and mobile users alike.
- Users of 084 and 087 numbers will have to publish the revenue share that applies to their number (details
http://www.ofcom.org.uk/static/numbering/s8_code.txt of amounts) under the new "unbundled tariffs" proposals.
All 084 and 087 numbers (with the exception of 0870 from 2009 until 2013/2014) are revenue share numbers.
The history is quite complicated, and detailed here:
http://en.wikipedia.org/wiki/Non-geographic_telephone_numbers_in_the_United_Kingdom#History_of_non-geographic_prefixes