For example, the area code of Guangzhou is 020 and the center number is +86 13800+20+0500.
Another example: the area code of Jiangmen is 0750, and the center number is +86 13800+75+0500.
The number of China Mobile SMS Service Center is +86 13800XYZ500.
Where XYZ represents the area code of your city, it should be noted that the area code here refers to the international standard area code, not the one with 0 when making domestic calls. For example, the domestic call to Dalian is 04 1 1, so the standard international area code here is 4 1 1(XYZ). Beijing is 10, and the last one is missing.
The general standard format of China Unicom is:
+861301XXXX500, please note that xxxx in Unicom SMS center number is not the area code to which SIM card belongs. This number is edited by Unicom, so it should be filled in according to different provinces. Generally, Unicom publishes the information center number by province, and some large and medium-sized cities will also publish it separately.
You can call the local manual station for the specific number, and they will tell you the specific number.