The “CDN Data Transfer Pay-As-You-Go Option” is available only for Tier 2 and Tier 3 plans. If you are using any other plan, please upgrade your plan first. For instructions on how to add the pay-as-you-go option,
see “Enabling the ‘CDN Data Transfer Pay-as-You-Go Option’” (https://ja.getshifter.io/shifter-support-documents/%e3%83%97%e3%83%a9%e3%83%b3% e3%83%bb%e3%81%8a%e6%94%af%e6%89%95%e3%81%84/pay-as-you-go-option-for-cdn-transfers)