Client account communication sent to the wrong person

Integer Capital has been sending me client account information (outstanding balances, Legal action letters) for one of their clients. I am not even a client of Integer Capital. I have asked them on numerous occasions to update their client contact details as it is sensitive information being sent to me, without any success (they do not even reply to my e-mails). I think it is really unacceptable behavior of a financial services company to be sending this kind of information to the wrong person.