Let’s keep this very simple…
NONE of your contacts, data or messages are ever shared to us, or shared to a third party by us.
Your data may be backed up for you to iCloud, Dropbox, or iTunes (depending on the app used, and only if you select those options) but we cannot access it.
A small amount of relevant information is included in support emails sent to us, for diagnostic purposes. You can read everything included before you tap “Send”.