To get a metro card in Mumbai, you have to fill a form and provide your Aadhar number. An OTP is then sent to your phone for verification. I never received the OTP. After about 5 minutes of exasperation, the customer support lady at Atrey Chowk metro station at Worli asked me to go stand near the escalators where the network signal would be stronger.
Five minutes later I was back at the customer support booth. Still no OTP. The customer support lady then gave me good advice: that I buy a standalone ticket for my destination. Which I did, for Hutatma Chowk for ₹40. As I got into the train, I was astonished to see it half-empty. This rarely happens on the Delhi metro. Certainly not on a weekday at 10 a.m.