Oppo
Turn Assisted Dialing (Roaming Assistant) On or Off auf Oppo
Assisted Dialing is a network feature in ColorOS that compares your SIM card's home country with the country your phone currently connects to. When it detects a mismatch, typically while roaming abroad, it automatically prepends the correct international dialing code to numbers you call.
The feature is meant to prevent failed calls when you dial a local-format number from a foreign network. In practice it can misfire: some numbers already include a code, some carriers report the wrong country, and some contacts only work without any prefix. When that happens, calls drop, go to the wrong destination, or show as invalid.
To check or change the setting, open Phone ➔ Menu ➔ Settings ➔ Assisted dialing and toggle the option on or off.
Turn it off if you notice extra digits appearing on outgoing calls while traveling, or if a contact stops connecting after you cross a border. Leave it on if you frequently call home-country numbers from abroad and want the code added automatically. If call problems persist after disabling it, check your carrier's roaming settings instead, since Assisted Dialing only affects how numbers are formatted, not network availability itself.