1) Welcome to the Party!
(Even if I'm late, you're still welcome. LOL)
2) when you post, please post your entire configuration including (but not limited to) your installation method and vicidial version with 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 "from scratch" you must post your operating system and should also post the .iso version from which you installed your original operating system. 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) Baby steps ... stage one: Is the problem with Asterisk or Vicidial or ...? Let's try our first simple test: Dial through the Vicidial server without using Vicidial, and then again using Vicidial. One dial 91XXXXXXXXXX directly from the soft phone (not in vicidial at all) or the proper dial pattern based on your carrier setup (preferably your cell phone so you can easily hear the quality) and then log in as an agent and use "manual dial" within the logged in agent screen to dial the same number (without the 91 ... because the Dial Prefix for the campaign should provide this automatically). See if one or both of those calls have clear quality.