If you use T-Mobile, this is something you may want to keep in mind.
The network is expected to stop working with a dozen older phones this month. If you use OnePlus 1 and Sony Xperia Z3, you won't be able to connect to the network from January 29th. This is due to a result of a network update that has affected the devices and are not able to receive a software update to allow them to stay connected.
They stated: "As a result of a network update going into place on 1/29/2021, we identified a small number of older devices that are not able to receive a manufacturer software update and as a result, these devices will be unable to establish a network connection."