Never seen such bad service before

Mtn's debt collectors started harassing me for an account that does not belong to me. I refereed this matter to Mtn hoping Mtn will inform the debt collector that they are harassing the wrong person since they have all my contact details, name and ID number in their file. The matter was referred to MTN's Legal Services for resolution. Instead of checking their records the lady who responded to my query now sends an email saying I should deal with the debt collector and provide an affidavit that they are harassing the wrong person. I fail to understand how and why I should be involved in mtn's mess and debt collectors for an account that belongs to someone else, which person has different ID numbers, date of birth, contact details and different account numbers from mine. Why does mtn think they can just dump an outstanding account on a person who knows nothing about the account??? Why should I now be running around doing affidavits for an account that i know nothing about?? How come no one at MTN has bothered to check their records so they can go after the right person owing Mtn??? I am appalled by such incompetence and bad customer service for a matter that is straight forward. I feel very annoyed and as soon as I get time I will be porting my number to another service provider. I have never seen such incompetence and lack of sensitivity for loyal customers.