Incorrectly charged

I have found that something went wrong as I was asked on 10/11/2017 to pay R24 per small parcel (x2) coming from Singapore. The weight of the parcels were 135 and 76 grams inclusive of pakaging, respectively. The value declared were 3.3 and 2 USD, respectively. The bill stated payment reason CN 22 and title "Income protection". The CN 22 is a custom declaration sticker. I could not argue with a staff (from Umtentweni office) as they were claiming that parcel have a "code". The bar codes start with S... that most likely for Singapore. They could not point what is a charge for as they didn't received new Post Office brochure. I want explanation, refund and apology. Would you pay some kind of flat "fee" that is more than 50% of the parcel value? Is this newly imposed fee another catch to curb on international on-line shopping customers? Where is free global market? If it so, my last order of R800 will cost me R220 in post office fees..