One of the most unprofessional outfit, telecallers call despite your number being paid for by ECS, they try to intimidate and extort money even for those numbers that have been put on safe custody after paying all dues plus safe custody fees.
Never had any such unprofessional behavior from Airtel, they are so well managed you don’t have to even bother to look at bill details. People wanting to port out to Vodafone beware. Unless it’s a case where other providers don’t have network strength.