Huawei
Enable or Disable Automatic Network Selection auf Huawei
Automatic network selection tells your Huawei phone to scan for the strongest available signal among your provider's networks and switch on its own. Once you search for a carrier manually and confirm it, EMUI locks the connection to that single network, even if it weakens later or your provider's own network becomes available again.
To restore the automatic behavior, open Settings ➔ Mobile network ➔ Mobile data ➔ Carrier. Confirm the prompt with OK, then enable Automatic network selection. The phone drops the manually chosen network right away and reconnects to your provider's default network.
Leave automatic selection off only if you deliberately need a specific roaming partner, for example while traveling in an area with weak coverage from your home provider. In that situation, a manual choice can give a more stable connection than the automatic scan.
Side effect of switching automatic selection back on: the phone briefly loses mobile data and calls while it searches and reconnects. This can take a few seconds up to a minute depending on signal strength in your area.