Complaint and need a full refund

I posted an urgent document from Postnet Durban to Postnet Plumstead, which was Dawn Delivery, supposed to get reach Plumstead at 9:00am on the 07/06/18, When the receiver went to collect the document at plumstead, he was told that they're waiting for delivery, he waited and he was told that they will call him as soon they receive the document, which was supposed to be handed in at 11:00am, He only received a call at 11:10am. the tender box was already closed at 11:00..When I called for a full refund, I was told to send an email.