Prices to call certain phone numbers from a BT phone can vary depending on which digits they start with and whether you are calling from a landline or a mobile phone. The other factor to take into consideration is what calls are included at what times with your specific call plan as well as other service charges.
Depending on which call plan you are on, To call a number beginning with 0370 for a business from a BT landline will cost 12 pence per minute with a set up charge of 21 pence. From a mobile, if you go outside the allowance in your call plan it will cost 35 pence per minute with a 1 minute minimum call charge and the call will be charged per second afterwards.