Hi Chloe,
A warm welcome to the forums.
"This is really frustrating as it says I have accessed my account using different devices, which I haven't."
If Plusnet state that your account has been accessed from multiple devices (IP addresses) then there is a fair chance that your account has been compromised and other people have been accessing your account from different devices. If that is the case Plusnet will have taken action to prevent further abuse of the services by changing your password.
Such action will have changed the password on your default Plusnet email address, that used by the user portal and the one required for the router to connect to the internet. Usually a Plusnet supplied router will auto update that password.
If what I infer is correct, I would highly recommend that EVERYWHERE you have used this email address as an identity for other services (Amazon, Netflix, Bank Account ... etc.) with the SAME password, that you URGENTLY change those passwords, ideally to something very different, certainly not the same password as you use for your Plusnet account.
Passwords for such accounts will not be changed by changing your Plusnet password, therefore those accounts (and the credit card details stored therein) are potentially also at risk of abuse.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
