i get calls from 647 numbers about once a week to my phone.  they are curious because the first six numbers match my phone number with only the last four being different.  It also says the calls are coming from New Zealand.  I don't have any connection to New Zealand whatsoever.  Is anyone else getting these calls?  

I tried answering and there's just silence.  Now I just let it go or ignore it and there's a silent 5 to 7 second 'message' left by them on my phone.

Other numbers that have appeared:
1647 580 1237