if you are using your phone as a presence sensor, you certainly added it in your devices and the first time it uses the name of your iphone (blabla iphone) or android phone (blabla Samsung S9+).
If you go to the device list view of the smartthings mobile app, you can edit the name by going to the device view and click the wheel at the top right corner. This should be the name used when you select the presence sensor setting of the smartapp.