Why does the long message replied by SMS business hall appear split and garbled?

Hello, an important factor in the normal reception of long short messages is the need for the support of mobile terminals. At present, the support of some models of mobile phones for long short messages is not ideal. The long messages replied by the SMS business hall cannot be correctly combined in such a mobile phone terminal. Usually, the short message content is displayed in several ordinary short messages (the number depends on the number of short messages), and each short message content can be displayed correctly, but a little garbled code may be added at the beginning and end. (The above content is only applicable to Guangdong Unicom users)