Before you invest money in anything you need to understand what you are investing in. Clearly you do not understand Steemit.com or the cryptocurrency STEEM/SBD.

You paid money via your wallet to promote a post that was considered spam and your post was flagged. No one at Steemit.com took money from your wallet.

Read the Steemit FAQ and Introducing Promoted Content.

When someone pays to promote content they are paying for voter attention, but they are not promised positive attention. If they get negative attention then their investment in promoting their article will be worthless. It is the possibility of negative attention leading to filtering that keeps the promoted content free from spam advertisements.
From Introducing Promoted Content.