When paying for help with the tax refund, It is not showing me the option to pick UK as my country, therefore i cannot enter my card details, what do i do?

I live in the UK and want to claim my tax back for my time in Canada last year. I am paying for help with my tax refund via turbotax. But when I try to enter my card details it is not giving me the option to choose UK as my cards billing address. What so I do?