The cause may be any of the following:
- "User ID", or "Email Address" may already be in use by another user.
Please register so that there are no doubles.
- "User ID" you are trying to use was used by another user in the past.
Please use "User ID" different from any current or past user.
- The user may already be registered to use the smartphone plan.
You will need to have this person cancel their smartphone plan. After contacting this user, have them log in to Sansan and cancel their contract from the Contract management screen.