In the US, that won't be the case. AT&T shut down GSM at the end of 2016. Verizon will be shutting down its 2G/3G CDMA network at the end of 2022. T-Mobile is a

In the US, that won't be the case. AT&T shut down GSM at the end of 2016. Verizon will be shutting down its 2G/3G CDMA network at the end of 2022. T-Mobile is also slated to shut down its 2G GSM network at the end of 2022. As others have pointed out, 2G GSM uses less spectrum (not for the same usage, but as a base) with 0.2MHz channels rather than 5MHz channels. There's been some stuff talking about T-Mobile running GSM inside the guard bands of their LTE network (dead space between channels). Still, it seems like they're also going to be shutting it down. T-Mobile's GSM network is pretty limited with maybe a third of the coverage of their LTE and 5G networks. It doesn't use any low-band spectrum so it performs pretty poorly. They also haven't been expanding it over the past 7 years or so, preferring to put their effort into LTE and now 5G. They did keep GSM alive a lot longer than AT&T (6 years longer), but it seems like the reasons for keeping it alive are dwindling compared to the cost.