Don't waste ad spend on already converted customers
Exclude active customers and users
If you are advertising through Facebook it's easy to make sure you don't show your ads to already converted customers. The targeting feature you are looking for is called "Exclusions". See below how to exclude a Supercrowd audience from your Facebook ad.
Step 1: Create your custom audience
Create an audience that represents your customers or users using any of the sources. A general guideline here is to be as broad as possible, for instance "Singed up before 0 days ago" will filter out all users that have signed up from the beginning of time until today.
Step 2: Activate audience in Facebook
After saving the audience, activate it in your current Facebook Ad Account.
Step 3: Exclude the audience
Edit your existing ad set
or when creating an ad set, click on "Exclude" in the Custom Audience pane.
Select the active subscribers, customers or users audience that you sent to Facebook in step 2.
When you save and publish the new ad set Facebook will make sure it's not shown to that audience!
Read more about Exclusion on Facebook: https://www.facebook.com/business/a/custom-audience-exclusions