Coming on the heels of the recent breach at restaurant chain P.F. Chang's, AT&T states that a third-party vendor managed to expose personal data for an untold number of customers earlier this year. According to a letter AT&T sent to its customers, the breach was caused by a service that unlocks cell phones for its customers. The company believes the service only caused the breach as a means of spoofing customer identities in order to unlock phones.

AT&T states that the data was accessed between April 19th and 21st, and have since taken steps to prevent it from happening again. "We recently learned that three employees of one of our vendors accessed some AT&T customer accounts without proper authorization," said AT&T in a statement sent to PhoneScoop. "This is completely counter to the way we require our vendors to conduct business."

The matter has been reported to law enforcement. At this point, it's unclear how many customers were affected and if their personal data is in any real danger. However, California law dictates that companies notify their customers when they suffer from data breaches affecting more than 500 people.