It is possible that you have had a product shipped to you that somebody wanted you to try for free. After all, it was a vendor you didn't buy from. I'm sure they got your info from the other vendors and if their product is good, they figure you'll order from them in the future.
It's happened to me in the past for other types of products, and I've e-mailed them as has been said, and been told we'd like to to try ours-no strings attached.
Join the NRA/ILA
I am the weapon; my gun is a tool. It's regrettable that with some people those descriptors are reversed.