No clear confirmation that my cards will work overseas.

Really worried about your very relaxed way of responding to me when I am super stressed about my travels and need clear confirmation that my mastercards will work when I visit the UK. Your agents on chat just tell me it should work and cannot provide a clear evidence. It does not show on my profile that my cards are open for international use in the UK and when I email your customer care, they simply close the ticket telling me I must call in to the correct business unit. This is a terrible customer experience and I have no confidence that I will be in a foreign country with cards that work. I just have to hope.