After the VoLTE function is enabled for some mobile card users, they cannot use the call waiting and call forwarding functions.
When the mobile card is in the position of the primary card, the call waiting and call forwarding functions can be set successfully, but cannot be set in the position of the secondary card.
Root Cause:
1. When a mobile operator enables the VoLTE function on the phone card of some operators, the call waiting or call forwarding status may be reset, causing this function to be invalid.
2. The primary card of a mobile card can be configured with call waiting or call forwarding, but the secondary card cannot be configured because the mobile operator needs to enable some cards through the data service. If the primary card of the mobile card is in the secondary position and the data service is not enabled, the configuration will fail.
Solution:
1. If the call waiting or call forwarding switch on the mobile phone is turned on but the function does not take effect, contact the customer service of the operator to check the network-side commissioning status, or request the operator to enable the call waiting or call forwarding function again.
2. If call waiting or call forwarding fails for the secondary card, switch the secondary card to the primary card, and then switch back to the secondary card.