Unknown debt

I am so upset with this school, somebody has used my name and ID numbers without my consent to register a child, My ex wife to be exact. And she never paid for the school fees of that child. Problem come when the school handed over the account to the lawyers to collect the debt. I have been trying to call them in their phone numbers on their website, no one is picking up the phone. Now the lawyers are in my case want me to arrange how am I going to pay R14 000.00. The school has the following numbers 011 693 5333/4 and 086 515 3219. None of the numbers is being answered. I have written an email to them a week ago. No response.