I am using a Twilio (Trial) account with number of Houston, TX to send SMS from my application. I am sending SMS to verified Indian number and that works perfectly. But when I am replying back to Twilio (already set webhook url as per documentation), it is not sending message back. It fails with message
Message not sent
Also the twilio number from which the message is received in phone is not shown.
Twilio developer evangelist here.
There are some restrictions when it comes to sending SMS messages to India. You can read up on our guidelines for sending SMS to India here.
The important part in this case is that:
Sender ID for international number will be replaced with XX-NNNNNN (2 letters followed by 6 numbers).
Basically, that means that the original sending number won't be sent to the user's phone. So, you can't respond directly to it.
You should be able to take your Houston Twilio number, enter that in the Indian phone and send an SMS to it which will be received by Twilio. You just can't reply directly to the message you sent from Twilio.
Let me know if that helps at all.