i got the game second hand.....
Okay, here's the answer - listen to me, and listen good.
PMD 1 doesn't use Wifi. You give the code to a friend and they rescue you. Or use a formula that I developed (it's in page 4, 5, or 6 of the Rescue Center Sticky; I forget which), then input the AOK Mail Code.
And what do you mean by "Random Mission"? If it's the billboard, it's for you to get your Rescue Rank up. Get 15000 or higher.