According to the official website of Apple Support, the iPhone 13 series does not support China Telecom's 2G/3G network, while China Mobile and China Unicom are not affected.
IT Home previously reported that sources said That China Telecom requires that from 2020, all 5G terminals should not be allowed to have CDMA frequency band and standard, as well as VoLTE switch; If the CDMA frequency band and standard have been reported, the time schedule for removal shall be specified. The final network access certificate and model approval certificate shall not allow the OCCURRENCE of CDMA frequency band and standard.
The removal of CDMA from the iPhone 13 series seems to confirm this message in part, albeit at a later date.
For telecom users, if the iPhone 13 series is in a bad location and cannot receive 5G/4G signal, they will lose their Internet connection directly.