You can change how much you charge per minute by going into your account, and at Settings -> Price, add the desired amount you wish to get paid per minute. 

In the same section of Settings ->Price, you can also have preferential prices for some members. To add a different price, click on the "Add member" button, insert the member's Skype ID, and the desired price you wish to charge him for future calls.

To learn more about "Select Minimum Call Duration" click here.

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