Bad DHL service tantamount to theft!

I recently sent an engagement ring to my son in Dubai. The ring was too large so he sent it back to me to be resized. DHL want to charge me R13000 customs duty on something that I sent to him and will be returned to him once resized!!! They were given specific codes under which they could clear the ring for resizing and return at no cost to me but they have just ignored the information. Then they tell me that it’s now in the government warehouse and I must pay another R5000 to release it!!! What kind of **** is this??