The display shows "You can't register as you are already using Ikkatsu Soufu service (bundling mail service) of each communications service company." on the online application screen for "Omatome Seikyu Service (combined billing method)."
回答
You cannot make contracts for both "Ikkatsu Soufu Service (bundling mail service)" and "Omatome Seikyu Service (combined billing method)" at the same time.
If you want to use "Omatome Seikyu Service," you need to cancel "Ikkatsu Soufu Service" with the communications service.
Click "here" for the contact desks of each communications company.