I agree with SXB - it is a CC matter.
Before pressing the call button, though, I would scan around and see if there is another seat to move to, as you may not wish to stay after your action.
I got attacked on another thread for saying that sometimes the CC could do more and I re-iterate it in this context.
Pax should not be allowed to get away with this type of behaviour and other pax should not have to act as Sheriff's deputies.
A few years ago, I reported a similar incident to an AZ captain after landing (mobile phone use during the approach, which was in gin clear VMC, but that is not the point) and he left the aircraft and went through into immigration to try and apprehend the culprit, with no luck. Pretty good response though.
My final sight was of him tearing a strip off the senior cabin crew member, presumably for not enforcing the rules.