Follow the directions below to manually activate Truecaller Assistant:
1. Disable your phone's Wi-Fi connection.
2. Open your phone's dialer, dial these two codes, and press the send button every time:
Note: If the message states call forwarding activation was a success then you are done. If it failed redial the activation code.
You will need to temporarily disable your phone WiFI and LTE to enable the service.
Go to your iPhone's Settings
Go to "Cellular"
Go to "Cellular Data"
Tap "Enable LTE"
Go to your Android Settings
Go to "Network and Internet"
Go to "Mobile Network"
Turn off "Enhanced 4G LTE Mode"