Paid twice for a delivery

Just for starters, i am a foreigner living in Prague so there is a language barrier. I made a payment online of 4230 kc to have a parcel picked up and sent, when the courier came, he tried to explain to me in broken english that i needed to pay. And when i asked him why he started saying stuff about box or whatever, so i thought he was saying i needed to pay extra for one of their boxes, but the amount was 4230 kc, the same as the payment i made online, by this time, the courier was getting fed up and showing an attitude and mumbling stuff in czech so i paid him the amount in cash. I sent an email to dhl just now asking them what the heck that was for and to look into the situation. Do you guys have any advice?