Only applies to existing AMEX card holders!. My friend holds a platinum AMEX cashback card and out of the blue called AMEX to cancel his card because of the introduction of the dormant fee. AMEX basically offered him £30 credit on his card not to cancel the card and when I tried my luck today I was offered £20 credit on my Platinum card too! Basically ring them up and tell them that you are sorting out your finances, found a better cashback card and worried about the dormant fee. ask if they have any incentives to keep you going. Don't straight away ask to cancel your card!
You need to ring the retentions team on 0800 0121 207. Don't ring the 0845 customer services number as they are only too happy to cancel your card. The credit depends on your expenditure in the past so if you are a huge spender then you are like to get a better credit! I am a very small spender and pay off all at once. Hope this helps some one out there