Debtsource

18 months ago I was told that I owe ADT money and contacted ADT was given a letter stating that the account was paid in full. I have now been receiving SMSs from Debtsource stating that I owe ADT money. I have emailed Debtsource the paid up letter and phoned ADT to sort this issue out. ADT said that they would let Debtsource know and I must ignore the SMS. I today have received another SMS from a Nelly at Debtsource stating that I owe money. She refuses to stop sending SMSs because ADT have still not let them know. Please could someone at ADT DO THEIR JOB and sort this issue out.