My understanding is that after being selected for arrival testing, they would keep calling you, every few days, until you provide them with the test results. This is mostly done using automated calls. I believe that eventually a human PHAC rep will call you to check if you already completed the test. It might not be advisable to avoid these calls, or refuse taking the test, as it might result in some fines, although I'm not sure how strict or fullprrof this system is.