The display shows "If you are already using the Ikkatsu Seikyu Service (single billing service) for each communications company, please register the single billing ID which is in your billing "customer contact numbers field".
回答
If you are already using the "Ikkatsu Seikyu Service (single billing service)" for each communications company, please register the "single billing service" main phone number which is in your billing "customer contact numbers" field."