Barclays Bank  -  Credit line decreased

Imagine my surprise today when after being a holder of a Barclay Bank Mastercard for many, many years, all of a sudden my credit limit has been reduced by $2,800. I have had a limit of $12,350 for years and I saw on my statement that they have lowered it to $9,550. Coincidently this is only about $250 above what I owe. I can see no reason for this. I have not used their card in over a year but I have consistently paid them early every month and I have never, ever missed a payment to them or to anyone else. I have been paying off my balances consistently. I have called the company and have been told that they sent me a letter explaining this. I have received no letter. So the representative read the supposed letter to me over the phone. Evidently they have reviewed my account and I am now a credit risk? A credit risk? I have been nothing but a loyal customer to them for more years than I can count. Their interest fee is outrageous and more than half of the payment goes to interest. I plan to report them to my Attorney General. A $2,800 decrease will definitely decrease my credit score which I have been working so hard to raise. This is ludicrous! Since this is the way Barclay Bank treats their loyal customers I will be taking measures to pay off my balance soon and then cancel my account.