Exotel is only a platform to send SMS. When we say we are a platform the end services or the distribution is taken care of by our partner SMS gateway providers and their operators.
Essentially, Exotel passes on all your SMS requests to our partners who have built the capable infrastructure to deliver these SMSes. Our gateway providers and their providers charge for delivering an SMS to a carrier's SMSC. This is an industry wide practice. Therefore, we are left with no choice but to charge you for the failed SMSes as well. Here are the rationales for charging:
1. In India Operators only charge for originating SMS, there are no charges for SMS termination. Let's say a message is sent from Vodafone to a jio number. The SMS travels through Vodafone's network and waits to get delivered to jio’s network (in the process completely utilizing Vodafone's network elements). So Vodafone says "You have used my network, now pay me!".
2. Secondly when the message (SMS) is submitted for delivery to the end subscriber, the system re-tries many times (for over 24 hours) to deliver the SMS. So, the network utilization for the unsuccessful messages is actually more!
3. In most cases of non-delivery, the SMSs are not delivered due to following reasons:
a. The called party terminal equipment switched off.
b. The called party terminal equipment out of the service area.
c. The called party terminal equipment out of memory (not enough memory to receive the SMS).
d. Invalid number dialed by the calling party.
So, operators make multiple valiant attempts to deliver your message and they charge us for it.