Virtual numbers, more appropriately DID (Direct Inward Dialing) is an ordinary telephone number routed over the internet by VoIP technology. We offer DIDs for USA and Canada to PSEB registered call centers. Each DID has two channels. Which means two of your customer/clients can call you at the same time without getting busy signal. You have to pay monthly rent for each DID, there is no cost on incoming calls. Whether you are inbound or outbound getting a local DID is crucial for your business. Not only your business associates feel at home but also it cost them local charges.
What about Vicidial
You can define multiple DIDs in vicidial inbound section. From there each DID can be directed to a voice menu, queue, phone or a voice mail. But routing is not restricted to these destinations only. You can have custom dialplan entry to emulate ring-groups and follow me features etc. The only thing left is to set that same DID as callerid in your campaigns. So that it shows up on phone CLI where you call.
Eyebeam is heavy-weight champion in terms of features but low on using resources, Many agents in call centers use and like this soft-phone. G729 codec available in eyebeam gives good quality also save internet bandwidth. You can read full review of eyebeam from here.
Zoiper a great interface softphone supports SIP Account and IAX protocol as well. IAX protocol said to bypass NAT transversal issues.
Full review and download available here.