What is a 1400 / 140-series number used for?

The 140 series is the number range TRAI has assigned for promotional and telemarketing voice calls in India. When you call from a 140 number, the recipient can immediately tell it's a marketing call from a registered business — which improves trust and reduces the chance of being auto-flagged as spam. Service and transactional calls use the separate 160 / 1600 series instead.