Should I pay to UPS?

Tweet

I have a new customer who asked me to sent X'mas tree samples to Greece in June. I suggested him to usd DHL as I could get discount from it.But the customer wanted to use UPS. The matter was customer did not have account at UPS but I have. When customer placed order to UPS, I seriously informed UPS if customer received samples but refuse to pay the freight, I would not take the blame even I have account with it. UPS said nothing and took away the samples. Now I receive claim from UPS that the customer really refused to pay freight, so UPS required me to pay for it. The freight is about usd4000, too much! What will you do if you were me?