What's the matter that the mobile phone won't automatically update the SMS center number?

Because the center number of each SIM card is different, this card is the default when it is put for the first time. If you use the mobile card for the first time and return the Unicom card for the second time, after you send a message with the Unicom card, it will automatically update the central number of Unicom at this time. If you send text messages when switching back to the original mobile card, you must manually change the center number, otherwise you can't send text messages. He can only automatically update the center number once on the mobile phone, which is related to the performance of the mobile phone itself, not the problem of the mobile phone.