How does Huawei p20 use telecom cards?

Do you mean using dual telecom cards? You can turn on the dual-card 4G switch, which is located in "Settings >"; Dual card management > enable dual card 4G ",which is turned off by default.

When the dual-card 4G switch is turned on, the secondary card can support 4G networks. If the secondary card is enabled with VoLTE (such as China Mobile Card), click "Settings >"; On the mobile network > card 1/2 network, a "VoLTE call switch" will be displayed, which can independently control the VoLTE function of the secondary card.

note:

1. If neither of your two telecom cards has Volte service, dual telecom cards are not supported.

2. Mobile customized version does not support dual telecom cards.

3. Full Netcom version, both cards have opened the telecom Volte service, which supports dual telecom cards. Set as follows.

Settings > wireless and network > turn on Volte HD voice call between two cards in the mobile network.

4. Full Netcom version, one card launches Volte service, supporting dual-card telecom. Set as follows.

The card without Volte needs to be set as the default mobile data card (Settings >; Mobile and Network > Dual Card Management > Default Mobile Data), and at the same time, turn on the high-definition call switch of Volte (Settings >; Wireless and network > mobile network > Volte HD calling).