I received my "FREE" out of the blue platinum card today to supposedly upgrade my "no annual fee EVER" gold card.
I think everyone needs to tread carefully before upgrading.
I checked out the original offer on the gold card I signed up to. The fine print relating to "no annual fee EVER" said "No annual fee will be charged on your credit card account for the life YOUR ACCOUNT REMAINS OPEN"
If you look carefully, you will see that the account number is different from the gold card to the platinum card.
I am no lawyer, but in my view this could technically mean by upgrading you have closed your gold card account and opened your new platinum card account thereby canceling the fee free offer and opening up the ability for Citibank to charge an annual fee in the future.
I will ring Citibank to verify.