I recommend checking out
cellmapper.net . It's not the most user-friendly site if you're not familiar with cell phone technology, but it's filterable crowd-sourced data on where towers are geographically situated along with reception test scores (mainly along main roads and highway). You can filter by cell phone provider, technology (i.e. 4G LTE), radio bands (i.e. 1900mhz).
I uploaded screenshots of the AT&T map, and separately, the Verizon map for you. I'm not familiar with Killingworth, but it seems VZW doesn't have any towers at all until you're near I-95 or go east toward Deep River. ATT has one tower right in the middle of Killingworth.
Best of luck!