What does it mean that cdma in SMS center does not support this function?

Some UIM wrote the service number of SMS center, and it is read-only.

Some can be set by themselves, and the default is +7. No texting, only receiving.

It needs to be manually changed to +86 1380 * * * 500 (* * * is the local area code).

UIM card is used to access CDMA network of China Telecom, and it is the symbol of access network system. The card stores the data needed to access the network, such as UIM ID, AKY value of authentication data, IMSI number, etc.