Contact the Internal Revenue Service and add an Identity Protection PIN to your SS#, you will have to have this pin in order to file taxes.
Good idea to freeze credit and getting a monitoring service. Sounds like you have Costco, if you are an executive member they have a monitoring contract with Complete ID. That's what I use, and it tends to report issues quick.
We were hit big time, finally had to change all of our checking and savings accounts too. But ours was a Dark Web breach, so they had much more information.