New Customer Promo Code Issue During Internet Checkout

Hello, I recently signed up as a new Xfinity internet customer. While I was finalizing my cart, a promotional code popped up on the screen. However, there was no field available to enter the code during checkout. I took a screenshot of the promo code offer, but when I contacted customer service, they informed me that there was no option to apply it and couldn’t assist further.
I’d like to request support in honoring the promo code that was presented to me during the checkout process. I have the screenshot available and can share it if needed.
Please advise on how this can be resolved or escalated. I appreciate your help in ensuring a fair and smooth onboarding experience.