The current data breach appears relatively low risk, although it could be used to tie your phone number to who you called. You’ll be getting a letter if you’re one of the lucky 200,000 who might have had their records accessed.
What was not accessed: “The data accessed did not include names on the account, physical or email addresses, financial data, credit card information, social security numbers, tax ID, passwords, or PINs.”
And the data that potentially was accessed: “The CPNI accessed may have included phone number, number of lines subscribed to on your account and, in some cases, call-related information collected as part of the normal operation of your wireless service.”
There does not appear to be any information about the dates that this breach occurred.[T-Mobile]