Its very unlikely they didn't think of that. Not all humans attached to phone numbers reside in the physical area of the area code.
Seems like he did actually call at night times.
1400 / 24 (hours per day) = ~58 per hour (round up to 60)
60 / 60 (seconds) = 1 per minute so nope, he was hammering at it 24/7 (unless my maths is totally wrong which is always possible).