Canceling PSA order

Hello, Just wanted to see if anyone has experience with canceling their PSA grading order after its already been shipped out and arrived at the center. I sent out an order and regret doing it so I emailed them about canceling about 3 days after the package arrived at their center. I did the $80 a card tier and saw on their FAQ that I can put in a cancelation request but it might not be honored so it has me pretty worried.

Has anyone successfully canceled their grading order after its shipped out before? and if so how was the turn around time for you?