I accidentally ordered a superfluous RC toy subscription. When I noticed the error a few minutes after it happened, I contacted the company, but they would to cancel the superfluous subscription or refund my money. There would be absolutely no reason for this, as they hadn't even had time to physically process the order. For everyone dealing with this company, here are you magic words: "That's fine, I will just contact my credit card company and request a chargeback." If the person on the end of the line is refusing to give you a refund, this will get their attention.
Here's a little secret: every time you chargeback a purchase via your credit card company, the merchant incurs a fee (usually between $25-$50, but can go as high as $100). Every time. So, if they are refusing you a refund on a $50 order and you chargeback to your credit card, they lose the original $50, plus an addition $25-$50. Because of this, they will be more willing to work with you.
Of course, there are some limits to this tactic. If the item you are buying is a clearance item or listed "as is", then that's a lot harder. Also, I am almost certain that their website terms of service will have some stipulation about items being sold as-is or some outrageous restocking/shipping fee. However, in the latter case you can still fight them via your credit card company. HobbyTron is almost guaranteed to have an usually high number of complaints attached to them in any CC system, so it helps your cause when initiating a chargeback.