You may create a Scam Accusation against them here in the forum. But submitting a complaint in Askgamblers will be better in that case. Betting site doesn't share the sensitive details in a public forum, but they will do that in the mediation center.
Exactly, they voided the bets, so you haven't won or lost any money. I have had the same many times that a bookmakers voided the bets for various reasons and there is nothing you can really do about it. I am wondering if a scam accusation is necessary if he hasn't lost any money.