$50 for 1 GB Internet Guaranteed for 5 Years??

Hi. I live in Brookline MA. Big college town. There was an Xfinity booth set up in the center of town soliciting incoming students to join Xfinity with a $50 for 1 GB internet guaranteed for 5 years.

I walked over to chat with them. I told them I’ve been a customer for a few years now. He said outright that these offers are usually for students and new customers, but he could get that deal for me and save me about $80 / month on my bill for 5 years. I even have a screenshot of the offer confirming this. I also have the Xfinity flyer they gave me (with his name and direct cell number) which says ‘Student Exclusive’ but he said they’re offering it to current customers to retain them.

So my question is simple. Is this legit? If so, great. I’d like to switch. If not, how can they be out in public soliciting with this offer?