Telkom and Hugo & Ngwenya Inc (********** debt collectors?)

I think Hugo & Ngwenya is a ********** collection agency. They are sending me claims for an outstanding Telkom bill that is not outstanding and they quoted an account number that isn't my account number.

When I tried to query it, they would not let me tell them what my issue is and said that they will look at the case first and get back to me. How can they get back to me if they don't know what the issue is?