[Freeswitch-docs] Free Switch with Dialler / Contact center suite and Billing system

Hi all, Have been going through free switch wiki and must say excellent product and on top open source. I am new to open source and looking to setup Hosted Freeswitch with Dialer / Contact Center Suite and Billing system. Looking at the wiki I can see there are fair few GUI / Dialler /Contact Center Suite availabel and there are two billing systems. However what is not clear is that which systems are compatible with billing systems and also no integration documents. I will really appreciate if any body can share some architecture/design docs if available which outline integration of freeswitch. Otherwise is there any use cases of free switch available? Thanks Gari