It's amazing that he answers his phone and expects it not to be someone like Gaiden or CVG. I hope he never learns his lesson because when the internet content is low the phone callers come through.
I believe it's for two reasons.
One, Chance craves attention above all else and he doesn't really care if it's all negative, it's attention and that's all that matters. For all his constant crying and whining of "Why can't you just leave me alone!?", he'd go insane if people just totally ignored him. This is why he "retires" from this that and the other thing and then has a "comeback" two hours later. It's why he's sworn up and down that THIS is the LAST TIME he's EVER talking to Marty ever again 137 times this year and then called him back 10 minutes later.
Two, it allows him to basically jerk himself off and indulge in his Raxx Lesnar persona. He knows he's less intimidating than a Cabbage Patch doll in the real world, but on the phone or the internet he can scream all the threats and racial slurs he wants without fear of getting what's left of his teeth knocked out. It's why he always barks orders at people when he's in rage mode.
"NO! HERE'S WHAT'S GONNA HAPPEN! YOU'RE GONNA SHUT THE FUCK UP AND LET ME SPEAK AND YOU'RE NOT GONNA SAY A GOD DAMN WORD, IS THAT UNDERSTOOD!? SO SHUT THE FUCK UP AND ANSWER ME! NOW! NOW! NOW!".
It's not a matter of him being too stupid to just set his phone to reject all unknown contacts, it's because he knows doing so would mean no more attention from anyone and no more getting to act like a hardass.
However he is too stupid to realize that he can't play the perpetual victim when he's the one who initiates contact with these people 95% of the time.
"Why can't you just leave me, my friends, and my family alone?"
"Chance, you called me"
"SHUT UP N WORD BOY! LEAVE ME ALONE!"