Need to cancel an old subscription associated with @optonline.net

1

Try to recover your Microsoft account that you used for the Microsoft 365 subscription using the process on this link.

https://support.microsoft.com/en-us/accounts-billing/manage/help-with-the-microsoft-account-recovery-form

2

If you are still unable to access that account, you cannot cancel the subscription yourself, the best option would be to contact your bank to cancel the direct debit for the subscription.

3

If that is not possible, this forum is just a user to user forum, no-one here has any account access, you will need to contact Microsoft Support directly, try using this method to contact their support.

Go to this link: https://support.microsoft.com/contactus

Select Microsoft 365

Click 'Get Home Support'.

In the box provided, type billing.

Press Enter, then on the next page, scroll down and click 'Sign in to Contact Support'.

Navigate to Microsoft 365 and Office - Manage my Subscription.

Select the 'Chat with support agent in web browser' option

If you go to https://account.microsoft.com/services , can you sign in with your e-mail (@optonline.net) there? Do you see your subscription listed? This would usually work even if you can't actually send e-mails using that account, assuming that the Microsoft account which is using your e-mail as a user name is still intact.

If the subscription is there, turn off recurring billing, if it is currently enabled, and then you should be able to cancel the subscription.

If the account is inaccessible, you have to try and recover it. See Dave's reply.