If you do not make a payment by choosing the "Extend Validity" option before the Validity expiry date (mentioned on the top right in your account), your entire existing balance will be invalidated. This also means your service will be suspended, Calls and SMSes through Exotel will be terminated.
We would suggest you make a validity payment before the expiry date to carry forward your entire credits to the next validity period so that you can use them later.
We'd be really sad to invalidate your balance, and would love it if you can make full use of this balance before that.
Please reach out to firstname.lastname@example.org for any questions related to your validity, We're happy to help!