Xfinity Agent asked for DOB and SSN for verification

Hello,

I called to ask questions regarding returning equipment for replacement and the agent helped me out. He said I qualified for a promotion for an Apple Watch because I am a gold customer and asked me to input my date of birth and full SNN in my phone’s keypad for verification. He insisted that he couldn’t see it and because it’s Xfinity,  I naively agreed, but know I soon realized that I probably shouldn’t have. Is this legitimate and should I be concerned?