I just discovered that the card issuer has reduced my credit limit and I no longer can charge anything. Can they do that?
Card issuers generally can increase or decrease credit limits without giving you notice, including reducing your credit limit so that you no longer have any available credit. If the card issuer does so, you cannot make any charges until you pay off some of your existing balance. However, without advance notice, the issuer will not be able to impose overlimit fees if you exceed the newly reduced credit limit, even if you previously opted in to the payment of overlimit transactions. In no event may the issuer charge overlimit fees if you have not opted in.