Microsoft I canceled my xbox live subscription by phone in 2015.I was told by their rep on phone my subscription was canceled ,They continued to bill me until the end of march 2018 florida

The only ripoff here is the one you did to yourself.

Back on the phone for hours and several peons later I was told that they only have the power to refund me for 3 months after taking my money without my knowledge for 3 years.
- Whithout your knowlege? WRONG.

The money just didn't vanish from your account. Every time it was deducted from your account, it was also listed in your account statement and transactions.  Meaning that if you did proper account management and reconcilled your statement that by law your bank must send you monthly(either by regular mail or electronically) means you had approximatly 36 chances to see this happening and stop it.  If you say it was too small for you to notice, then you can't come back and say they owe it back to you because you didn't care enough to stop it earlier.

Now, don't get me wrong if you cancelled it and they did not, you have a valid complaint and the next month it was charged you should have been on the phone to clear it up. But after 3 years this responsibility(and blame) shifts to you.  You are lucky that they gave you a credit for 3 months, as even the Federal Fair Credit Billing Act only allow disputes up to 60 days.

I highly suggest you go through the rest of your accounts to make sure you don't have any other companies taking money out.