Issues-ofDialAsist,
Please double check that the region for your device is to the region that you're in. You'll find that in Settings > General > Language & Region.
If you're using any type of VPN or security software, please temporarily remove it, restart your iPhone and test again.
You also mentioned not being able to turn off Dial Assist. Have you restarted your device or reset the network settings? When you reset network settings, "Reset Network Settings: All network settings are removed. In addition, the device name assigned in Settings > General > About is reset to “iPhone,” and manually trusted certificates (such as for websites) are changed to untrusted.
- Cellular data roaming may also be turned off. (See View or change cellular data settings on iPhone.)
- When you reset network settings, previously used networks and VPN settings that weren’t installed by a configuration profile or mobile device management (MDM) are removed. Wi-Fi is turned off and then back on, disconnecting you from any network you’re on. The Wi-Fi and Ask to Join Networks settings remain turned on.
- To remove VPN settings installed by a configuration profile, go to Settings > General > Profiles & Device Management, select the configuration profile, then tap Remove Profile. This also removes other settings and accounts provided by the profile. See Install or remove configuration profiles on iPhone in this guide.
- To remove network settings installed by MDM, go to Settings > General > Profiles & Device Management, select the management, then tap Remove Management. This also removes other settings and certificates provided by MDM. See “Mobile device management (MDM)” in the iOS Deployment Reference."
Thanks.