FYI, Many "money back" offers on diet pills are notoriously difficult to get your money back, so be skeptical of money back offers unless you know someone personally who DID get their money back (not just said they did on an anonymous website - some companies will actually pay folks to make false reviews. No one would expect a disatisfied review as being fake, but it happens with money back guarantees because the company wants you to think it's money back guarantee is genuine).
A lot of folks have posted horror stories about companies not only not givng them their money back, but making future fraudulant charges and continuing to send the person product they didn't order.
I've tried dozens of prescription and otc weight loss products, pills and powders, and even injections, over the past 4 decades, and in my experience most don't work. Those that do, stop working after a short time and/or have unpleasant side effects. The better they work, the more unpleasant and sometimes even dangerous, the side effects.