Why should I pay the customs penalty for DHL's mistake?

I purchased a product from the UK and 2 weeks ago it arrived in South Africa via DHL. Using the online tracking system I was able to ascertain that it would be delivered to my place of work between 14:00-16:00 on Friday 22 September. I waited and waited an it did not arrive, at which point I contacted the DHL customer services call centre. I was told that the package was not delivered because it was awaiting customs inspection and that I needed to send through certain invoices and other relevant documentation. I did this within the hour and had upheld my side of the bargain by the time office hours closed that Friday. I was told by the DHL representative that he would contact me as soon as he heard from customs regarding any duties that would have to be paid in order to have the package released.

I emailed the DHL representative on Tuesday 26 September to follow up, and the next day he reported that he was still waiting to hear from customs. I then emailed on 28 September (no response) and on Wednesday 4 October (still more silence).

Eventually on Thursday 5 October, I spoke to him telephonically. Within minutes he had contacted customs and they had sent on an invoice for immediate payment. Not only did the invoice include the horrifying (but expected) duty fee, but also a penalty fee of R2201!

The DHL representative was unable to explain this penalty, as he appears to have no knowledge of the way that customs works. I imagine the explanation lies in this clause which is included on the invoice in bold lettering:

"According to the South African Customs Act any clearance not effected within 7 days from the date of arrival in the country, will result in your shipment being transferred to the Government State Warehouse pending clearance (additional charges will be incurred in this instance). DHL will not be liable for any claim resulting from such handovers."

The representative forwarded a query regarding the penalty to someone higher up the ladder at DHL but she has not responded to him or to me. This morning when I sent my daily email to follow up, I got an out-of-office reply to say that my trusty DHL liaison person will be on leave till 23 October.

Now there are several things about this situation that really make me angry:

1) Most importantly, I should not be held liable to pay the customs penalty if DHL did not send on my invoice timeously. I was assured that a DHL representative would contact me and, according to the online tracking system, my parcel has been "awaiting customs inspection" for 13 days, so there was no notification or invoice there either. As I have mentioned, my failure to pay was not for lack for trying on my part (4 emails in total, 2 phonecalls and daily checking on the online tracking system)

2) DHL representatives should have at least a basic knowledge of how customs works so that they can avoid clients being penalised for not paying their duty fees within the stipulated 7-day period

3) DHL representatives should have the courtesy to respond to all emails and queries sent to them (2 of mine went unanswered)

4) The DHL representative I have been dealing with sent the query email on to his superior twice yesterday, but it seems that at no point did he pick up the phone and speak directly to this woman

5) This was the cherry on top - the DHL representative that I have been dealing with went on leave without resolving my issue and did not have the courtesy to tell me that he would be handing the issue on to someone else. Very poor customer service if you ask me.

I hope that by writing this complaint on Hello Peter I will be able to get in contact with someone from DHL who is competent and able to resolve this issue by providing me with information regarding the penalty and a satisfactory solution which will result in me receiving my long overdue package without having to pay fees that I am not liable for.