I you have an Exotel Coupon, you can redeem it by doing the following:

1) Go to http://my.exotel.in/pay

2) Choose the Discount/Coupon Code option from the accordion

3) Enter your coupon code and click redeem

Once you've done that-

Prepaid accounts: You'll see that your coupon amount has been added to your Exotel balanceĀ 

Postpaid accounts: You will see that in your forthcoming bill, a discount worth the amount on the coupon is given to you