These services are essentially identical. They both bypass existing carriers to use an alternate infrastructure to carry long distance calls at cheaper prices. So what is the difference between dialaround and call back?

Callback:-

When you use a call back service, you dial a pre assigned number and hang up. This then triggers a return call to that number which enables you to switch to a different service and use this services switches to make the call. In other words your callback service literally calls you back on their network thereby bypassing the local system and theoretically saving you money. A callback call can also be triggered via the internet. Please click here for a more explicit description of call back services.

Dial around:-

A dialaround service (lets call it service "B") exists in parallel to your existing service (Service "A"). It allows you to use the services of another carrier by first dialing an identification code which says to Service "A" "I am now using service "B". You can have a whole series of dialaround services all co existing if you wish; and as long as the correct identification number is dialed - that specific service will be used for that specific call. Please click here for a more explicit description of call back services.