Capital One Capital One 360 Account Refuse to close account McLean Virginia

In March 2016 I deposited a check I'd cashed for a friend of mine and I signed under his signiture, Capital One accepted my deposit and posted it the following day, On day 3 my account was frozen due to what they at Capital One said was fraudulent or suspicious activity, I called at least a dozen times to close my account, I've sent several letters requesting my account to be closed and funds sent to me, every month I receive a statement with my account balance, I have received an additional $5.28 in interest added to this account, my balance as of today 02/16/2018 is $1.325.20 I get my statements in the mail each month, I have written to FDIC and called several attorneys but have gotten nowhere. I am at my witts end and can't figure out how to close this account when Capital One will not even answer my written letters demanding my funds and account to be closed. I have no idea who to contact about this matter. They refuse to close my account or reverse the deposit.