Android
Turn On or Off Assisted Dialing auf Android
Assisted dialing rewrites the number you dial when your phone detects you are outside your home country. It inserts the correct international prefix and country code automatically, so calls that would otherwise fail with a busy tone or an Invalid number error go through as expected.
Android decides whether to apply this rewrite based on the SIM home country you configure and the network country your phone currently detects. If those settings are wrong, the feature can add the wrong prefix or skip it entirely, which is why checking the toggle after a SIM swap or a trip is worth doing.
Where to find the setting
Open Tap on Phone ➔ Open the Menu ➔ Tap on Settings ➔ Tap on Assisted dialing ➔ Enable or disable Assisted dialing. On this screen you also pick the default country of origin that Android uses as the reference for the automatic prefix.
Turn the toggle off if you dial mostly local numbers that already include a leading 0 or a specific prefix that assisted dialing keeps overwriting. Turn it back on before international trips so outgoing calls and text messages to your contacts connect without manual country codes.