Malwarebytes Antimalware offers a free and a paid version. Under no circumstances are you charged before you can remove malware.
I suspect that you have actually been conned into installing some malware, rather than the true program. For example, googling reveals a site called Anti-Malware-2010.org/Malwarebytes which is a typical con and nothing to do with Malwarebytes Anti-Malware.
You can get the genuine FREE version here:
http://www.malwarebytes.org/mbam.php