With effect from 1 August BT will drop the premium from calls to 0870 numbers - see
this pageThe same page announces that the rates for chargeable calls will be increased from 1 October, as will the call set-up fee. This is simply the expected further effort to get people onto inclusive call plans.
All premium rate service numbers and revenue sharing 0844 numbers are excluded from calling plans.
Calls to 0845 numbers are included in BT calling plans. This has something to do with the odd situation with BT and 0845, which makes it cheaper than calls to geographic and 03 numbers, despite costing BT more.