Please note that ALL models in the myFirst Fone series are compatible with 5G SIM cards, but they are not 5G devices. Therefore, when a 5G SIM card is inserted, the watch will NOT BE ABLE to use the 5G network.
Instead, myFirst Fone R1 and R1s watches will use the 4G network, while the myFirst Fone S2 will use the 3G network.