(head in hands)
Please, please talk to somebody who understands the tech behind this before saying this to anyone else. It makes you sound ignorant.
Today's "landlines" use the exact same infrastructure as cell phones do; fiber optics. The box in your neighborhood that translates "phone lines" (which really don't exist any more beyond the neighborhood level) into fiber optic is just as vulnerable as the cell infrastructure. More, actually, because the cell phone towers generally have backup batteries.
If you want true redundant communications, please study up and get your ham radio license, and join a local ham radio club so they can show you what to buy.
I am on a small providers system and most of the people I talk to are on that system and that is who I will want to talk to.