Booked then they wanted more money

I booked/paid for two tickets through cheapoair. I recieved booking #, itinerary etc. Then hours later they sent me an email/and called to say I had to pay twice the amount I paid. I called the airlines which had my reservation (United) and they said the reservation had been cancelled by cheapoair. So they sold me tickets, demanded more money for ticket I bought and paid for. What a scam. I bet it happens all the time. This is pure FRAUD. I've called Fox news, ABC news, BBB, ASTA, etc. I'm not letting them get away with this.