In order to make international calls from your Slingshot mobile you will need to purchase the $15 Cash Allowance add-on. This add-on is a one off charge that will give you $15 of credit that can be used on ad-hoc services like international calling. It will be charged to the Slingshot invoice following its purchase.

Once the add-on has been purchased simply dial out like you would from your home phone - don't forget to enter in the country code of the country you're calling though!