Why do new customers get better deals the long time ones?

I've been a customer for over 25 years. My plan is too high, and I don't use my home phone anymore. I put in my address on the Xfinity site while signed in and it gave me a TV and Internet deal for $45! Wow great, everything I need! I go to add it to my cart and checkout, it won't let me, it says invalid customer name. I was told by the chat representative to call, the lady on the phone said it sounded like an internet deal and try to figure it out on my own. I used separate browsers, and it kept doing the same thing.
The last agent I talked to said they couldn't do anything, I offered to send the screenshot of the deal and they said they can't receive them. Then offered me a package at over $100 dollars. 
I feel at being a customer for this long, I should be able to get a decent price once every 25 years! and I would have done it online if I could have! The customer service has really gone downhill. Spectrum is offering the same deal and I'm switching.