I moved my address from USA to UK.
When I did this my two chase BA 2 for 1 vouchers vanished from my account.
I called BA and they said I had to be in the US to use them.

So I left my account for a little bit, decided on where I would use the voucher, called BA, changed my address back to US and redeemed a voucher.
Then the same day called BA to change address back to the UK one, as I don't think you can change it that often, said I did it by mistake.

They changed it back to UK one.

A few days later I got a letter from AMEX UK saying that my BA AMEX account had to have a UK address in my BA profile.

lol