Negligence and refusal of refund

I'm highly irritated I request a Refund over 15 days ago & I was told it was paid to someone elses account.. High level of negligence didn't verify the account if it's mine now I'm told they waiting for a refund from the other yet it was not my fault they deposited the money in the wrong account after I sent an email with the account details to be used. No one called to check if I had changed the account number. Yet the bank confirmed its not my account.