Telephone scam?

On the assumption that you don't know anyone in Sri Lanka, block the number on your phone.

Block the number.
I have a iphone and I have set ‘do not disturb’ between certain hours so that it rings silently during those times.
However it WILL ring if the call is from one of the contacts I have identified in my ‘Favourites’ (so that I don’t miss an emergency call from one of my close family and friends). It also will ring from any caller who rings twice in quick succession (so that I would hear a call from a hospital or any other emergency contact I do not have listed)
I think you were just unlucky to receive a scam call.

AN iphone (obvs!)

I have blocked it. My phone is set to do not disturb so I don't know why that call got through.

It’s because they called back immediately. It’s a nuisance that you were disturbed but sensible that the DND setting allows a repeated call to ring in case of anyone trying to cal you in an emergency. If it happens again, like some landline scam callers persist by using other numbers, you may have to switch off your phone for a few nights so they don’t get through and hopefully they’ll give up using your number.

I switch my phone off at night, as once I take my hearing aids out I wouldn't hear it ring anyway.

I switched on my phone one morning last week, and it said I had 2 missed calls from a strange looking number at 1.05am and 5.00am. I just blocked the number.