I use the card primarily to pay US suppliers (why I'm with Amex) and they will quite frequently put a hold on transactions (over 2K) for "security checks" -- which used to mean a 30 second call to CS to get it authorised, sometimes late in the evening due to the time difference (the Indian call centre will not be able to do this directly, they will have to defer to the UK, I am sure). I often need goods dispatched by the merchant the same day so expediency is important. UK service was always superb.
Last time I was put through to India the guy got fixated on his flowchart and tried to get me to register more contact numbers, he kept asking if the UK "01..." landline I finally provided was a mobile number, and he has probably messed up my billing details as I have one US number on the card specifically for US authorisations (tel number is checked like a post code in US). Sometimes the line is so weak you can't hear a word they are saying.
It is just a disappointment, I was always very impressed by their customer service. I have never dealt with a bank or credit card company that has a foreign call centre so for Amex, who seem very customer focused, to do this is surprising. Anyway, I think the green card is the only one to have been offshored? Is this correct?
Only way to know for sure is to enter your card number on the CS number and see where it leads. . .