Sure you can. And yes, if the player has a history of violating the Fair Play Policy, they do take action. Click Contact top right of any Help & Support page. Here, I'll do it for you:
https://support.chess.com/customer/portal/emails/new
/help
Sort:
Oh okay, so we should report using this form and not /help?
Yeah, this is mostly for members to give advice. You really need to file a "ticket" to get anything done. Did a message pop up after the game saying your opponent "may have violated our Fair Play Policy" ? If it did, then the computer noticed the disconnect already and you really don't need to do anything. There is a "bad player's pool" that frequent disconnectors and abusers of all sorts get thrown into so they end up playing each other.
Does /help actually work? Can I report bad players this way (that dc after losing).