They will be able to understand English. I would not use the term "chargeback," though (and I certainly wouldn't use romanian- for god's sakes). Credit cards- the whole concept of being able to keep your money in a bank and not have the bank blow up, or the idea of "credit"- the idea that your lender will be alive tomorrow is a very, very new idea in many of these nations.

I would make you sentences as simple and choppy and possible: I have not receive my product from ______ conf #.
Would you be so kind, to help me receive my money back?

The "Would you be so kind" seems a little over the top--but it's a direct translation of a phrase often used when asking a favor in many slavic languages, and should there be any doubt in whether I know what I'm talking I about, I graduated with high honors in Russian, have 5 years of post-baccalareate education in Slavic and East-European language and literature, and have taught dozens of students who have become Russian majors after their classes with me and come back to ask for reccomendations.

I also somehow managed to figured out the ingredients in the train stop food stand in the Slovak republic and get my family something to eat, as well as getting them on the right train in Czech. I don't actually speak either of those languages- I speak Polish and Russian. That website is in a Slavic language.