Why does the number of the SMS center change?

For China Mobile, the number of SMS service center is+861380xxxxx500, where xxxx is the long-distance telephone area code where you are located, and if it is less than 4 digits, add 0.

For China Unicom, the number of the SMS service center of China Unicom is different from that of China Mobile, and the rules are complicated. Only by looking up the table, Shandong+86130101765438 or 0086130.

After setting the number of SMS service center, you can test it. Edit a short message and send it to yourself, and check whether the setting of the short message center is correct. If you can receive it normally, you're done. This is also the easiest and quickest way to test the setting of SMS service center.