Mint Mobile says it has suffered a data breach, one that exposed personal data of an undisclosed number of its customers.

According to BleepingComputer, Mint began sending out emails to impacted customers on December 22.

“We are writing to inform you about a security incident we recently identified in which an unauthorized actor obtained some limited types of customer information,” reads the email.

“Our investigation indicates that certain information associated with your account was impacted.”

The outlet reports the exposed data includes Name, Telephone Number, Email, SIM serial number, IMEI number, and the service plan the customer is currently on.

Fortunately, no payment information was compromised since Mint does not save credit card numbers. The company also says customer passwords are protected by “strong cryptographic technology,” meaning they were not compromised.

As BleepingComputer points out, T-Mobile previously announced plans to purchase Mint Mobile. It’s unclear if/how the data breach will impact the deal.