How does Lenovo default to SMS?

Usually, if the device does not have a third-party SMS installed, its default SMS application program is the address book program attached to the fuselage. If you need to set the third-party SMS application installed later as the default, you may need to enter the settings of the software to try to set the default.

If it is a dual-card mobile phone, you need a default sim card for texting or making phone calls. You can go to Settings -sim card management to set up calls, text messages, etc.