Under the 'Your Phone Number' tab you will see the Exotel phone number assigned to you and your pin. When you call your Exotel number, you are required to enter the pin in order to get connected to the flow you have mapped the number to. Similarly, to get connected to your SMS flow, you need to enter your pin number before the message to get connected to your SMS flow.

For example: if you want to send an SMS to your Exotel number with the message "sales", and let's say your pin number is 9999999999 then the message text should be "9999999999 sales".