Hi
You should be able to transfer calls between Featurelines, please see the user guides (at the bottom of the page) for more information. Or you can call the helpdesk on 0870 513 3399 if you are having problems.
If you get a mobile then you may have to pay for calls from the Featurelines to the mobile, unless you have One Plan Plus which includes intra-business calls at no extra charge, so you can call/divert/transfer to your BT mobile from the extensions at no charge.
I hope this helps
Kind Regards
Fiona
BT Business Forum Moderator