Account In Arrears Incorrectly in my name and listed

I am having a challenge with ADT / Fidelity Security Services since last year and it is affecting my credit record. They inputted my ID number in an account (PHA00920) which does not belong to me.

My account number is PHA01531 which is active and fully up to date. I have received confirmation written confirmation from Chedwin Chetty (Team Leader at ADT) on 02/11/2022 that this is resolved and the correct ID number was captured with mine removed and that they have sent a request to the credit bareua to fix this.

To my Suprise today I get a letter of demand to pay and when I call ADT / Fidelity again, my ID number is still attached to this account in arrears. I have been on hold for a long period to speak to Chedwin to no success