Non-delivery of important document

A friend recently sent an important letter via postnet Three Rivers, Gauteng, South Africa to the local post office in Stanger KZN, South Africa...its been almost two months and I havent received anything, and whats worse is that they have no idea of what happened to my document all they say is that it should be in transit and if i dont have a tracking number then they really can't help me. This has become a real inconvenience and my concern is that if they were not capable of delivering this document to me then why did they agree to doing it.