1) Welcome to the Party!
2) As you are obviously new here, I have some suggestions to help us all help you:
When you post, please post your entire configuration including (but not limited to) your installation method (7.X.X?) and vicidial version with build (VERSION: 2.X-XXXx ... BUILD: #####-####).
This IS a requirement for posting along with reading the stickies (at the top of each forum) and the manager's manual (available on EFLO.net, both free and paid versions)
You should also post: Asterisk version, telephony hardware (model number is helpful here), cluster information if you have one, and whether any other software is installed in the box. If your installation method is "manual/from scratch" you must post your operating system with version (and the .iso version from which you installed your original operating system) plus a link to the installation instructions you used. If your installation is "Hosted" list the site name of the host.
If this is a "Cloud" or "Virtual" server, please note the technology involved along with the version of that techology (ie: VMware Server Version 2.0.2). If it is not, merely stating the Motherboard model # and CPU would be helpful.
Similar to This:
Vicibox X.X from .iso | Vicidial X.X.X-XXX Build XXXXXX-XXXX | Asterisk X.X.X | Single Server | No Digium/Sangoma Hardware | No Extra Software After Installation | Intel DG35EC | Core2Quad Q6600
3) This is a support question, not a "General Discussion". I'll move it to the support board. Next time ... please post in the appropriate board or purchase pizza for a moderator. LOL
4) Your subject line is pointedly vague. You probably should have used something more like "Echo on some calls and Agents hear ringing when they receive a call".
5) Echo is hardware related, as a rule. What sort of headsets are you using? If you're using the sound card from the workstations the agents are on, consider a USB headset.
6) You did not state the method of making these calls. If you have a manual dial campaign, of course they hear ringing, LOL. I'll assume for the moment then that these are autodialed calls. Vicidial does NOT connect calls to an agent until two things happen: first the call MUST be answered. second the sound on the channel must be live. Only then will the call be transferred to an agent (this avoids wasting agent time). Challenge: What happens if your carrier lies to you about the answer? And then plays a "ringing" sound file for a little while? Of course, then they invoice you for the fake call and everyone's happy.
Um ... get a new carrier. You should have at least three for a functional system anyway. You can try to discuss it with the carrier, of course, some will clean up their act (since it's often not actually them but an "upline" carrier that they do not control).