Unlimited Data Unavailable

Hi,

Data caps will be going into effect on 1/1/21 in my area. I was looking into the unlimited data add-on. I saw a promotion saying that I could add it for $0 for 6 months and $30 thereafter while using my own equipment. When I go to add it, it says that it is temporarily unavailable. Can somebody help me? I've seen that several others have had this issue over the last several months. If I am reading the website correctly, I think I need to add this by 12/30 to get the $0 for 6 months. I see there are options for using the xfi gateway, but I am not interested, I want to use my own equipment.