Poor service at the Post Office

I sent someone to the post office in Vanderbijlpark with an affidavit and the correct paper's to renew my license disc and she told me that the lady at the post office told her that she cant assist because I did not write the reason why I cant pay the disc by myself which I think it was so unnecessary, cause I clearly stated on the Affidavit that I am sending someone to pay on my behalf.