Blackberry SIP VoIP client

Hello all , We are looking for someone who can develop a sip client like fring, skype or trufone over blackberry for us where our users can make calls over wifi or GPRS.. we do not need IM but just voip calls including options like able to call from address book , recent calls . Please do not bid if you cannot provide me the blackberry app you developed before i accept your bid . If you have no idea abt blackberry or if you have never developed any application do not bid . if you also have expertise in iphone and symbian it will be much useful as i need same application in othe platforms too but Blackberry is my first preference. Thanks and Regards