They charged me more after I had checked out...

When I placed an order online with his company the inital final cost was $15, after using a discount code.  There was no problem with this code when I checked out and my credit card was charged for this amount.  A few days later they emailed me with my total and it was $5 higher.  I told them that this was not correct; when I checked out, I agreed to the $15 total not, the $20, they must have made a mistake.  Then they told me that the discount code was expired (how convienent) and that would have to charge the higher amount. So they took the $15 charge off my credit card and replaced it with the higher amount.  This is a ploy to get more money out of a customer after the fact and it is dishonest.  The amount of your order should stay the same after you leave the website.  I will never do business with them again.