Google Voice is a free telecommunication service which provides users with a single number to call anywhere in the world, and also online voicemail. The search engine giant has confirmed that users would be able to port their own phone number as the one for use on the Google Voice service.
Google has announced that number porting is available for all existing Google Voice users. Google Voice is a free service that lets users make PC-to-PC voice calls worldwide. As a Google Voice user, you'll be given a unique number for calling anywhere, and also online voicemail (to your inbox). However, it is kind of awkward to juggle between your own mobile phone number and your Google Voice number. Thankfully with the implementation of number porting, things are a lot more convenient.
All you need to do to port your number is log in to your Google Voice account, go to Settings and click on “Change / Port” next to your Google Voice number.
However, porting your number to Google Voice costs US$20 and is usually completed within 24 hours. According to Google, there may be additional charges incurred, including early termination fees from your wireless carrier. Well, this only applies to users in the US though. We can only wait for this to be available worldwide.
Source: Google Voice Blog