When you are using a test key with our API, only the connection will be tested; no messages or calls will be sent out. This allows you to check that your API has been set up correctly without using your credits or balance. 

Note: Test Keys are not supported in our Conversations API.

If you want to start sending messages, you can create a live key for this. The live key will call our API, send out a message, and take the correct amount from your balance. You can use the live key in combination with the test credits in your account.