You can verify the "customer code" [お客様コード] on the My au (Web).
Please refer to the following for detailed steps.
Regarding the name of the number you need to verify, please confirm that it is indeed "Customer Code" [お客様コード].
Tap on "Smartphone/Mobile Phone" [スマートフォン・携帯電話].
Tap on "Contract Details/Procedure" [ご契約内容/手続き].
Tap on "Registered Customer Information" [お客様登録情報].
Check the "Customer Code" [お客様コード] here.
It is required when performing procedures such as modifying your contract in writing or exchanging eligible third-party points for Ponta Points.
Has your problem been solved?