One card issuer is sending alerts to help you spot errors and bogus charges on your statements, and some banks offer apps to switch your debit card on or off. Thinkstock By Jessica L. Anderson, Associate Editor From Kiplinger's Personal Finance, October 2014 Thieves are coming up with ever-more-ingenious ways to gain access to your credit and debit card numbers. And, let’s face it, mistakes happen. So card issuers are making it easier to police your accounts.SEE ALSO: Get a Free Credit Report More Than Once a Year Most card issuers have zero-liability policies for fraudulent charges on your credit card. Bogus transactions on your debit card can take longer to resolve, even when your bank doesn’t hold you accountable (see Safeguards for Debit Card Users). Beefed-up monitoring services are alerting customers to questionable charges, and a recent survey by CreditCards.com found that 4 in 10 regular credit card users have received such an alert. Some charges aren’t necessarily unlawful, but they may be unwanted. For example, two in three customers overlook potentially duplicate charges, says Capital One. Its new alert service, Second Look, flags such charges and sends an e-mail with instructions on how to question the transaction, if warranted. Second Look also highlights subscriptions that renew automatically and flags increases in recurring charges, such as a cable bill that might have risen without your noticing. Debit cards are slated to get the service soon. Advertisement Of course, thieves can’t use your card if they can’t get it to work. New mobile-banking apps allow you to switch your debit card on or off. Deter scammers by keeping your card turned off and switching it on only when it’s time to make a purchase. Tech firm Malauzai provides the capability to about 80 community banks and expects to have partnerships with a number of larger banks by the end of the year. Capital One, USAA and online bank Simple have introduced their own on-off switches in their mobile-banking apps.