hoow can I make and receive calls With USA and Canada by using a PBX account, Acrobits softphone, and Google chat?
I've had good luck with Acrobits Softphone... it's a SIP soft phone for iOS.  Once you have an appropriate VoIP/PBX account that supports SIP clients, you can use google chat to get your calls into the PBX.

It definitely has some noticeable lag, but it is certainly better than nothing.  

You can get a free VoIP/PBX account at pbxes.com (I have no affiliation).