I'm having some difficulty finding a clear answer to this. Essentially my parents want to switch landline providers because they currently pay $72/mo ($55 + fees/tax) with AT&T. Normally you could just make the switch to VoIP but the issue is they have an old alarm system with ADT that's connected through a landline. They spent a small fortune back in the days getting sensors on every window and door so they'd like to stay with ADT, but the problem I'm running into is that there's no actual landline providers. I thought it'd be like switching energy providers where there's several to pick from, but everything I'm finding is VoIP based, and I'm not sure how that would work with their current system. Any advice?