MK Supplements Fraudulent Charge on my AMEX Card Mill Creek Washington

On April 13, I noticed a charge for 59.95 to my AMEX account from MK Supplements. I never made this charge nor did I know this company at all. I immediately contacted AMEX to dispute the charge. On May 17th AMEX denied my claim saying that MK Supplements had proof of the transaction! I never bought anything from MK Supplements.
On May 18th I received a plain enverlope with a bottle with several stamps on it and no markings except a return address of a PO box in Mill Creek Washington. I immediately mailed it back unopened to the PO Box and called AMEX again.
This time AMEX said they would investigate as a fraud charge. They have changed my credit card number as a result.

On May 18th I filed a complaint with the BBB or Western Washington.

Someone has to stop this illegal activity

George
Orlando, Florida
U.S.A.