Samsung doesn't know what data your phone sends any more than (for example) Dell does when you send data via one of their computers.
Your phone service provider (Vodafone, EE or whoever) can't see the data either, because it's encrypted.
Only Google Play gets the information, which is securely held in an encrypted form. Some free apps (indeed, many of them) offer 'in-app purchases', which are entirely optional. However Google Play needs to have your card details available in case you choose to use such facilities.