Experiences with ipad, voip and bell 3g?

[KAD3190]

Having got our office PBX (asterisk 1.6, home built) finally accepting registrations from my ipad (using media5 phone app), I was testing various connections. No problem talking using a WIFI connection, but when connected through Bell 3G, I could establish a connection but no sound would flow (either direction).

I thought it might be some 3g filtering on the part of Bell?

However, I tried a different connection from the IPAD to my home (regular bell line), via our office PBX asterisk system and it worked (noisy, but it worked).

Just curious as to other's experiences using the 3G data network as a voice system from their iphone/ipad.

TIA, K