CITY OF TSHWANE CANT FIND MY HOUSE PLANS

I purchased my house in June 2013, which is situated in Montana Gardens. I want to do building extensions and have been trying hard to retrieve the current house plan or any plan for this house. The City of Tshwane branch in Sinoville cannot find the plans in their records, the branch in Akasia referred me back to Sinoville, the Head Office in town also referred me back to Sinoville. All roads lead to Sinoville that cant help me??? I need urgent intervention in this regard.