I would have upgraded in a heartbeat for that deal. But they offer a 12 month plan for current customers but the price goes up after the 12 months, this provides no benefit to me in the long term. Even though I have been a loyal customer of HSI for over ten years, changing plans just to find a bargain is too much of a hassle. I would have been a guaranteed customer for life on one of their upgrade plans with the price guarantee. But I guess I'll stick with my current service at the regular price.
Have you called customer service and specifically asked for this option? That is my recommendation. Sometimes you have to specifically ask for the plan by name to get it as some plans are Honor Do Not Offer.
I already asked them in the Contact Us support chat. They said that promotion was only for new customers. I really wanted to upgrade my HSI service with the price guarantee for life. But they offered a $29.99 price for a year to existing customers. They won't budge on the price guarantee for customers that have shown loyalty to their HSI. FYI I have had the 1.5 mbps plan since it was first offered that was ten years ago. I don't want the hassle of hop scotching my isp just to save a few bucks.