If you receive an email or a phone call from the CRA saying you haven't filed your return, it could be a scam. To check the status of your return, log into CRA My Account.
You can also review the CRA's tips on the Slam the scam – Protect yourself against fraud page for recognizing a scam to help determine whether the email is from the CRA or a scam.
If the CRA hasn't received your NETFILE submission, it may be that you didn't finish submitting your return.
Slam the scam – Protect yourself against fraud (Source: CRA)