UMA (Orange only)
if you got no signal but have access to at least 128kb internet or higher (think it only needs about 32kb or 3KB/s bandwidth when in phone call, but make sure your not uploading or downloading at Full speed on an computer at the time when in call or it get choppy voice)
if you got BT broadband it works 99% of the time (if the below is done), it may work with your band of router at all wifi will connect but UMA will not switch on (not with my edimax cable router but i can See the 3g tower from my window so coverage is not an issue for me at my house)
switch the wifi off and on the phone if it does not connect to UMA (my BB 8520 was quite reliable at UMA, not so much 9870 ok once you get the UMA connection working aka switching the wifi off/on from the phone menu),
set wifi to channel say 1, 6 or 11 and Set wifi mode to b\g Only, that is best compatibility mode(other option to set to WPA2 only if all your devices support it but make sure you copy the key down and paste it back in, if you do change the WPA2 password change the SSID as well so it forces you to reconnect all your devices or you have issues with other devices)
wifi b\g\n mode on the BT home hubs are bit flaky (and some other routers as well) and does not work very well with blackberry phones or laptops or iphones (or most wifi products even BT disable it when they connect to it) as it can drop the connection or have packet loss every 10-30 secs
as i had one customer who was on three and they let him cancel his contract for free even thought he was inside the 24 month part (only did 7 months) got an orange blackberry same one i had with me that i tested on his hub he can now walk into the house and it just switches form GPRS to UMA on the fly when he gets close to his house,when he comes out it switches back to GPRS, (this is also in an phone call as well but does not always work)
The phone Has to Be Orange Branded blackberry (any with wifi) or android (that supports it) to have the UMA, if its an unlocked blackberry phone that was not on orange UMA will be disabled on the phone
the UMA is not perfect, if the voice keeps on repeating or you get call failed after 5 seconds your router is not allowing packets throw correctly (like the edimax 6574n) or the ISP your using is lame (Sky routers)