Stuck Front Screen on S7 Edge

[PhilG23]

My son has just gone on holiday and has rang me (not on his phone) with a Stuck front screen.
It says Free Cleaner on the top left. 3 menu dots on top right only giving Settings options. then not actually any settings.
The current Time
3 Speedometer widgits RAM - STORAGE - BATTERY
Then Swipe to unlock.
Swiping just moves everything off the screen and leaves a black screen.
Obviously any search of free Cleaner just bring up the usual expected rubbish on google so im hoping someone here has seen it before.
I've tried to do the power and Volume Down reset but no luck.
Any ideas before he gets back and I take it into the Samsung store?

 

[B. Diddy]

He should be able to force a shutdown by pressing and holding Power and Vol Down for about 15 seconds. Once it's shut down, power up in Safe Mode: https://support.t-mobile.com/docs/DOC-28008. In Safe Mode, go to the App Manager and look for any suspicious app that might be related, and uninstall it.