Unreliable DHL

My company in South Africa had to ship important documents for a tender in a foreign country. DHL was contacted and advised the latest time by which the document had to be handed in to DHL in order for us to meet the deadline. The date and time were confirmed when the documents were dropped off at the DHL office. The tracking showed that the documents arrived in the recipient country the day before the deadline, however they did not attempt to delivery the documents until after the closing time for the tender. Eventually they only delivered the following week but we were disqualified due to the documents being late. A credit note was requested for poor service and a missed opportunity for our business. Our Account Manager at DHL confirmed later that a credit note would be passed and an apology letter was received from DHL. They then backtracked on the credit note as there were "inter-departmental" issues, and offered a consolation free shipping on our next shipment. This was not acceptable as they have, on several occasions, delivered late thus disqualifying on future earnings. We have thus decided to rather to fly personnel to drop off documents personally as DHL is completely unreliable, their assurances are meaningless. I would not recommend anyone to make use of DHL if they are concerned about meeting any deadlines.