I received an email from myaccount Optus on 12/10/2017. It states that "Your new SIM for your mobile number ... is now active." It stated my mobile number in the email.
I did not request a new SIM nor have I received a new SIM. I am still using a SIM that I received at the beginning of the year.
On the same day that I received this email I also received a text from 321, the voicemail number, stating that - "For security, we have reset your Voicemail PIN."
To me these two occurences are related to one another. I deel that somebody out there has a SIM with the same phonenumber as mine.
How do I go about getting a new SIM with a new phone number? How could this have happened?