I have an iphone 4 running on an ipad sim with data only and no voice. I am currently using textfree for voice and text over wifi and 3g. It works great, but I have no voicemail. Does anyone know of a solution to use the iphone with a VOIP and sip provider that provides text, voice, caller id and voicemail? I have access to a gizmo5 account if that is needed. Thanks for the help.