I just click on Shop a Subscription section and it does give 3G $15 & $25 plans.
I'm fully aware that there are $15 and $25 plans. My points was about your statement to use a computer to view them. I do realize the a phone, a tablet, or any type of electronic device that can process instructions and make calculation can be considered a "computer", but most people consider a computer to be a device that is running a Windows or Mac operating system. Public Mobile is only advertising an app as being avaialble for iOS and Android. As such, going to website's Shop section does not show the $15 and $25 plans. The app doesn't show the regular Shop website.