Re: Can I add 3 sim pay monthly accounts: one for me one for my son and one for my partner?
Was the SIM Only set up in your name? If you are the account holder to this number, then you can take out another SIM Only number BUT they have to be in your name again. You will then be able to manage all three numbers under one online account.
You can take out SIM Only deals once logged into your account under Plan and Device. That way they will be added under the same email addess and account holder and saves a call into 789.
If you want them registered to separate people then they will all be on separate online accounts.
Alternatively, if the number is registered to your son, why not log into his online account and change the email address that is linked to him there and let him have his own email address. That way you can use your email address again for yourself and your husband.