Constantly harassing

How does this company continuously harass clients who's contract expired months ago ...they forget to mention this what the fine print say as long as they can get the sale .This is there current harassing message they send a person even when you told them telephonically you can't pay for something you don't have use of " NOTICE OF ARREARS !URGENTLY PAY AT YOUR NEAREST ZONE FITNESS BRANCH OR FNB ACCOUNT NUMBER ***, BRANCH 210655, REF ID OR CARD NUMBER. REGARDS ***/***"