Yup, I had the same experience. You need to pay a ₹349 deposit and then you’re set within 10 minutes. I migrated all 4 numbers in my family (all in my name) to postpaid and the process was seamless. Luckily you don’t need a sim swap, as 2 of the numbers are used by my parents who live in another city.
There’s a limit that you can’t migrate more than 2 numbers belonging to the same person in one day, so I had to visit the store twice.