At the very least you must always post your Vicidial version with build. You should also post the installation method (which you did: Goautodial 3.0), however I get the impression that it may not have been you who actually performed the installation so it's tough to tell where you stand with that portion of the project.
It sounds like asterisk has not yet fully loaded. You may need to post the actual CLI output (always the best way to go) which includes the command and the error. If you are trying to type "dial" at the asterisk CLI, that's your problem (that's not how Vicidial works). There is an asterisk CLI command and configuration that supplies the dial command, but you aren't being clear that this is what you are attempting so I'm not sure what's up there.
In this case, I have a couple suggestions for you:
1) Perhaps you should consider installing with Vicibox (from Vicibox.com) instead of Goautodial.
2) When you install (via Vicibox or Goautodial) please use the provided PDF (Vicibox) or Wiki (Goautodial) from beginning to end. After you have completed the installation process and need to configure the server for use, you switch to the Vicidial Manager's Manual. There is also some help in this regard in the Goautodial Wiki, but I don't spend a lot of time there since that's still Vicidial and yet not upgradeable to the latest version without losing all the Goautodial logo/addons ... so Vicidial is still the better bet. Vicibox is unquestionably more thoroughly tested and upgradeable and has much more support available. (On the other hand, if you MUST have CentOS, Goautodial is the best method)
3) Explain why you are asking about the Dial command in the CLI. As this does not appear in the documentation, you got here somehow ... I'm not clear as to whether you built the system and it failed and you found this in the CLI output during examination or whether someone else built the system and you read somewhere that entering this command in the CLI is a "good test" for something.