Why is the ringtone of Apple's mobile phone the default? Can I change it?

Can be replaced, the specific method is as follows:

First click the "Settings" icon on the phone desktop, as shown in the figure below.

2. After entering the phone setting interface, go down to the menu, and then select the "Sound" option, as shown in the figure below.

Third, you can choose the ringtone you want to set after entering. Take setting "SMS ringtone" as an example, click to enter.

Fourth, after entering, you can choose the type of SMS ringtone.