Issue related to Communication

Hi all, I am asian. I am having this very problematic issue. In my day job, I provide production support for a large application. We have weekly calls with our clients. The clients are mostly European. One of them's surname is Welsh I am having a real hard time understanding their accent. I want to tell them that I cant understand thier accent. If I say so will it bad thing to say. That is, will they get offended by it ? I am asking this question as many here are from the European continent. Regards, Ronald