Keep getting threatening smses although my account was paid before being handed over

<p>In July I got an account from NHLS.</p> <p>I paid my account in full in September.</p> <p>In October I got a message from MBDCS informing me that I have been handed over.</p> <p>After I kept getting messages I have on numerous occasions sent proof of payment to both MBDCS and NHLS . I have called them explaining and I have asked them to stop harassing me.</p> <p>Eventually I got hold of one of the agents that told me my account with them shows that I do not owe them anything. He went on the explain that the automated system has a problem and I should just ignore the messages.</p> <p>This is nou a month later and I keep getting threatening messages.</p> <p>I have had enough of this!</p>