Do you always check the URL of the site you are about to send money to.
It is possible that the site that you are visiting is not the site you wanted to visit. It is also possible that the information you are typing - passwords and so on are being monitored. The solution for this is quite simple.
Always - always check at the very least that the site you are visiting has the site lock symbol in your browser input bar. This may be on the left or right of the bar depending on your browser with ultimate security being where you can read the name of the company in the bar.
This means that the company was verified by an independant authority who warrants that the site you wanted is the site you are visiting.