Android
Turn On Automatic Network Selection auf Android
When automatic network selection is off, Android stops handing your connection over to your carrier's tower by itself. This usually happens after someone manually picked a network abroad, or after a failed handover left the phone locked to one operator. The result shows up as a Searching... status, missing signal where coverage should exist, or a roaming icon that never clears.
The setting lives per SIM. On dual-SIM phones, you have to repeat the steps for each card, otherwise one line keeps searching manually while the other reconnects automatically.
To turn it back on, go to Settings ➔ Network & internet ➔ SIMs, pick the line under Choose a SIM card (Dual SIM) if you have two, and switch on Automatically select network.
Leave the toggle on for daily use. Only switch it off temporarily if you need to force a connection to one specific operator, for example when your default carrier has an outage and a partner network is reachable instead.