Banks don't sell Bitcoins, stock exchanges don't sell true bitcoins yet (Robinhood allows you to buy but you can't withdraw and use the coins yet, they say this feature is coming) and you never want to leave your coins on an exchange unless you are day trading. Gemini is my exchange of choice I am US based and they report everything and are insured against theft, they have tried to get an etf but were just turned down recently, they are however extremely legitimate.