Recycled number too inconviniencing

When we moved to a new flat in February this year, Telkom gave us a new landline number. Unfortunately we get phone calls on that number every too often, that it has now become a bother. Sometimes the calls come at night and most times, when we are extremely busy. I called Telkom today and the named consultant said that unfortunately it seems that the new number was recently being used by another person. And I have to pay R180 to change to another number. I just don't understand why Telkom would recycle numbers that haven't been inactive for a reasonable time and then charge me for wanting to change. Maybe I am being unreasonable here, but that's not Ayoba!