Quite possible though is a significant disruption of one of the many services like LNP which are implemented via SS7 and shared by all carriers - there is indee

Quite possible though is a significant disruption of one of the many services like LNP which are implemented via SS7 and shared by all carriers - there is indeed a complex set of inter-dependencies between carriers that are all somewhat generically referred to as part of the SS7 system, several of which are required to successfully set up a call or deliver a text message.