If a person's mobile phone was designed to work with $4$G technology, what will happen when a $5G$ network is rolled out in their area?$-$

They will still have service through the $4G$ network for at least several years.

Their phone will automatically upgrade itself to work with the rew $50$ network

They will kase service as the $4G$ network is deactivgted to make room for the $5G$ network.

Their phone will only work. when they are put of range of any $56$ netwerks.

I don't know this yet.