Parcel not delivered a month after it arrived, call center puts me from department to department and no one can help or give me info, then promise to call us back and never do (apologies mean nothing without action)

Shipped a package from Germany for our business, on the 25th of September 2017 the was due to arrive and supposedly was due to be delivered on the 11th of October 2017, however an invoice for the package never arrived from DHL, called them ahead of time to see what the delay was with the invoice so that we could pay DHL, no one at DHL call center could tell us why we had not received an invoice, or who to speak to in order to get an invoice re-sent, call center agents keep promising to mail us and explain who we need to speak to or send us the invoice and weeks later we still have not received a single mail from them, called again to try to track the parcel as none of the online example tracking codes match our tracking code, they now tell me that the parcel was delivered on the 11 of October 2017, how is this possible as we have not received it nor signed for it, and have still not even received an invoice to pay DHL, i now assume my package worth tens of thousands of rands is either ****** or lost some where in South Africa, and DHL is giving us the run around to cover their tracks and hope we forget about the package (as if), Please DHL sort this out, all we want is what belongs to us.