To use mobile data, you need to set APN matching the corresponding service provider.
(USIM insertion, overseas roaming, etc)
Settings > Wireless & networks > More > Cellular networks > APN
• When APN is not set, it tries APN in the basic APN list sequentially to match
the corresponding USIM, and mobile data may be activated with delay.
• When APN is not set, if it is connected with APN that is not actual data, you cannot use mobile data.
(You need to set APN corresponding to the fee table. For fee table, contact service provider.)