Bandhan bank is not a payment bank. It is a fully bank and got license from RBI to function like SBI, PNB, Canara bank, IDBI etc.
Bandhan bank has not yet present in all over India, as it was a micro finance and it has major operation in eastern part of India like Odisha, West Bengal, Jharkhand etc.
So every body can not get the benefit of banking service.
Regarding 6% interest in savings account, now days most of banks are providing this interest rate but they have certain condition like minimum balance need be maintain beyond 50,000 to 1,00,000.
This scheme is just to attract the customer.
I am giving a best suggestion to get more than 6% interest from your bank.
Most of the banks now providing a flexi account where you get benefits of both savings and fixed deposit.
Suppose you keep 1 lac in flexi account you will be getting 4% interest for 25,000 and rest 75,000 will give you benefits of 8% interest.
You can withdraw that 75,000 amount any time with out any fine or charges.