Please note that Freepik, Flaticon, Slidesgo and Wepik are different projects from the same company. Although your user credentials will be valid for all three sites, premium memberships do not work the same way. If you acquire a Premium plan for Freepik, this will only give you access to the premium resources from Freepik and the other way around.

If you want to have access to the premium features for the other sites, you will need to buy a Premium plan for Freepik and another premium plan for the website you want to use as premium user. 

With regards to the payments, since both sites are part of Freepik Company, the confirmation emails about your subscription and the charges that will show in your bank/Paypal statements will all come under Freepik Company name, even if you have bought a Flaticon subscription.