How to  make calls from gmail account? How the charges will be collected?

Google has brought the facility of making calls from the Gmail e-mail account.  With this it is competing with the Telecom operators like AT &  T, Verizon communications and web calling services organizations like Skype.  Presently free calls can be made to America and Canada phone through Gmail.  Call charges will be very less for other countries.  Calls can be made through the ‘Call phone’ option from the Chat Buddy list which is in the  Gmail.  Charges for this are collected from online accounts of the users.  Top up of these accounts is possible with  credit card, Google informed.