They've done similar to myself by upping the interest rate and leaving me a take or leave it email. That's the flexibility of so called plastic friends for you. ! ....
I use mine and clear it before interest is due, therefore it doesn't affect me as all I require is the free legal consumer protection offered on transactions paid for when using a credit card.
In time, they will need your custom and by then it will probably be too late, as most of their ex-loyal customers will have voted with their feet and gone "rate tarting" elsewhere for better rates. ?