[Asterisk-Users] OT - how to get BT to present a number

[Asterisk]

If anyone can help me with this I'll be soooo grateful :)

We have a isdn30 line, with a DDI range. We also have 2 business units that 
have separate 0870 numbers that are mapped onto 2 DDI numbers.

I would like to be able to present these 0870 numbers from the business 
units so that the correct number is displayed on a callerid, or when 1471 is 
dialled.

BT claim that I can only have a single presentation number on the entire 
isdn line. Pipex claim that I can have a presentation number allocated to 
each DDI number that dials out. On the same ISDN line ! They simply take 
over the line, it's still fed into the BT exchange.

Short of moving to Pipex, what can I do to get BT to allow me to do this ? 
Who do I need to speak to ? What techno speak must I give ?

Julian