Cheapoair.com Watch out for This internet company Internet

I made reservations on the internet with Cheap-o-air.com and I called them to confirm.  The person on the phone told me the return date was not valid.  (1st RED FLAG.)  I continued to make the reservation on the phone for a return flight that was valid.  The person who helped me quoted a total price of $586.20.  What they didn't tell me is that $75.00 of that is a SEPARATE fee from Cheap-o-air.  My credit card shows two charges - one for the airfaire of $511.20 and one for $75.00.  I immediately called Cheap-o-Air to ask what the $75 was for.  They said it was taxes and fees from the airlines.  The person I talked to said to me, "Didn't _______ quote you a total price of $586.20?  I said yes.  (By the way, the first person who answered the phone I couldn't understand...they are all foreign--so I had to get another person to help me!)  But when I saw my credit card I immediately saw the extra charge.  Their website claims to include fees and taxes on all their flights so why would there be a separate charge of $75.00???  This is an unauthorized charge on my credit card that I will definitely contest.  DON''T use this company.  They are a RIPOFF.  I will be calling United Airlines to confirm whether or not my flights are even valid.