When using dual cards, the default network card is the main card and the non-network card is the secondary card. If you want to switch the main card, please refer to the following methods:
1. Pull down to open the notification center, click the Switch data SIM icon, if the icon shows card 1, the SIM card of card slot 1 is the main card, and if the icon shows card 2, the SIM card of card slot 2 is the main card.
2. Settings > SIM card & mobile data > Default SIM settings, select the card you want as the default Internet access card and this card as the main card.