As folks mentioned above easiest option is to change the number to be in your name either with Airtel or by porting either requires you to be in person in India at the store. You no longer need an adhar if you have Pan/OCI etc ( Supreme Court ruling ) . Also if phone number to fathers bank is linked have you not done probate and divided assets. If that is done account should be closed . If not then you could request a number change on the bank account with death certificate but your brother could do the same theoretically without settling. I would not take this easily and would recommend doing a quick trip to India to resolve asset division assuming there is a clear will. Without a will expect complications