I don't think you can. I've never heard of anyone doing it and if I remember correctly the disclaimer when you purchase it says a refund will not be possible because it will start immediately.
If you cancel it early you still get the full amount of time you paid for and don't get any money back, it just stops it from automatically renewing.
But if there is a way then it will be by contact customer support, so I suggest you try that. They might say no, but it couldn't hurt to try and maybe if you explain your reasons they'll decide it's a reasonable request and figure out a way to do it.
PC EU player | She/her/hers | PAWS (Positively Against Wrip-off Stuff) - Say No to Crown Crates!
"Remember in this game we call life that no one said it's fair"