You can call a customer directly from Tally via Skype. To set this up go to Settings > Custom Customer Fields and create a new text field called 'Skype ID' or similar (anything containing the word 'Skype). In the Other Info tab of the customer details screen you will then have a box to enter their Skype ID and next to it a Skype icon will appear. Click the icon to start a Skype call to the Skype ID entered.