Fishy billing of Vat & Duties

Ref: Y ********** 966 We couriered a small parcel in November to the UK valued at 474 Pounds. The courier charge/quote from UPS was 135 Pounds. We were charged VAT on a value of about 800 Pounds. We have been trying to query this for months now and the service and attitude is shocking to say the least. We have been told that because our Commercial Invoice did not have the courier charge on it, that customs thumb sucked the landed costs and charged us on an extra 324 Pounds instead of 134. UPS charged us for the freight so obviously HAVE the exact freight costs for when they clear customs. NO ONE bothered to tell us to redo the commercial invoice and add the UPS freight charge to it. We emailed the invoice AND attached copies to the shipment. TEBOGO could have simply emailed us, told us to add the 134 freight/courier UPS cost and resend the invoice. It would have taken minutes. NO ONE refuses to give us proper answers, documentation etc. They just don't care! I will NEVER use this dreadful company again. I demand the customs clearing documents that UPS completed in UK and need to know why they did not do their job properly.