let me answer your questions
for 4 seater call center you really dont need any CRM
what you need is
a manual dialer i.e vonage.com,voixs.com ,
superphone.com etc, a bandwidth like 256 dedicated (take it from micronet)
its not necessary to take bandwidth from PTCL
i done have any experience of voice chatting paid solution ,infact i also want to know about that .
hope it helps