Samsung has started rolling out the January 1 security patch for the Galaxy S7. Its rolling out over the air in the UK and will expand to other regions. You can read up on the fixes by the January patch here.
The Galaxy S7 duo was updated to Oreo in May 2018, which will be the last major software update (the phones were released in March 2016). This update just fixes security vulnerabilities (3 critical ones in Android, 4 in the Samsung software).
The Galaxy S7 edge is still on the December security patch, but its update will probably start rolling out soon as well.