Providing incomplete information regarding a renewal of license disk

The I would like to complain about a bad service I received at the Post Office in Brakpan North on the 4th of May 2016. I went to renew my license disk on the 30th of April 2016. Upon arrival I provided proof of residence as required according to their notice boards. I was informed that I need to obtain an affidavit as the property is not registered under my name. On the 3rd of May I got this affidavit done at the Brakpan Police Station stating that I am still residing with my mother and she is the registered home owner. I then went back to the Post Office on the 4th of May and one of the tellers checked all my documents and concluded that I have everything required and can proceed to the queue. When I arrived at the till I was then informed by another teller that I have incomplete documents and must now provide my mother's copy of ID. I then requested to know why I was not informed of this when I came around the first time and why are we not getting the same information from the employees as they work for the same company. They wouldn't budge and I still left there without renewing my license disk. Can the Post Office kindly ensure that the employees feed the correct information to the customers and outline properly what they require instead if making travel endless trips.