I guess that's the only possible course of action for now. In the CIC website, it is mentioned that sometimes, they would call by phone if they need to request more info or documents.
https://www.canada.ca/en/immigration-refugees-citizenship/services/protect-fraud/internet-email-telephone.html
Again, chances are, it was a prank, but let's see tomorrow.
Just a question, did you have to submit any PCC from any country (that is, did you live in any other country besides Canada for over 6 months within the past 6 years or since you became PR)?