This is actually Indigo. They called me to inform of a flight schedule change, which they had already informed me of through several emails and WhatsApp messages. Please, one message is enough.
Automated message claiming to be from IndiGo informing that my flights had been cancelled or rescheduled. The flight details hadn't changed so I contacted IndiGo and their customer services confirmed that the number is not used by them. Some sort of scam.