Does BytePhase send SMS through Gupshup if I have not set up another SMS provider?

Yes, for shops in India. When no SMS integration is active and marked as primary, BytePhase sends your SMS through Gupshup automatically and draws on your BytePhase SMS balance. If you later make Twilio or BulkGate your primary provider, your SMS go through that account instead, and only one SMS provider is primary at a time.