The 20 GB for $20 Data Plus option is only available on the $28 /mo Base Plan.
20 GB for $20 is a Plus option and not a Boost. You cannot add 20 GB to your plan several time through this Plus option in the same month.
However, you can add additional data on top of your Base Plan for $6 /GB using the plan customization tool available in the CirclesCare app under the “Customize” section.
If you need quick data boosts at the end of the month, you can always use our Boost feature available on the CirclesCare app Dashboard to give your data a pick-me-up!