Even when the show came out roaming wasn’t a thing. Roaming has nothing to do with esims and it has to do with which cell network you are connected to. In the American context, if your provider is Verizon but where you are you can only connect to T-Mobile towers then you are roaming.
Some of a telco’s biggest customers and biggest vendors are other telcos.
MVNOs operate on MNO networks. MVNOs have agreements on access and usage to use MNO networks. MNOs also have agreements with other MNOs to roam on each other’s networks. These are called access charges and access revenue
Even when the show came out roaming wasn’t a thing. Roaming has nothing to do with esims and it has to do with which cell network you are connected to. In the American context, if your provider is Verizon but where you are you can only connect to T-Mobile towers then you are roaming.
MVNO networking is more common now even with the big providers where the roaming is "free" because they lease or trade bandwidth.
Some of a telco’s biggest customers and biggest vendors are other telcos.
MVNOs operate on MNO networks. MVNOs have agreements on access and usage to use MNO networks. MNOs also have agreements with other MNOs to roam on each other’s networks. These are called access charges and access revenue