Peer 2 peer calling, 2 differnt locations in the world

Can anybody help me how to make calls between 2 diff locations in the world with out a staticIp? Is it possible? Is there any other ways to do this? I wan to use a IP/normal phone at one end. I am thinking of phone adaptors. I had internet connectio in both locations. I want to setup server at 1 location. I am new to this forum. Currently I am using voip service in both locations. I am thinking if we can elimante the voip provider. Can we use asterisk by seting up DYDNS service?