Prosperitas very ********

I was contacted about 7 years ago, because of school fees that wasn't paid by my ex. Cynthia said that, according to law, I have to pay half of it and they will get my ex to pay her half. Last time I spoke to them Cynthia said that they won't follow up with my ex wife and that I will be paying everything. When asked what changed since the first arrangement, she only said that they won't send a summons to her, but if I stop they will send me one. Why is it that the law, in this case, can be bent to only one side? My ex doesn't have to pay anything and where ever she gave my name, with no knowledge by me, the places only attacks me? We've been divorced for almost 17 years and I always paid my maintenance. Can't prosperitas follow the law, they threatened me with and said both are responsible for it? I can't even stop it, because they keep on changing the naming of the deduction.