Ios 14 ringtone disappears automatically.

1. Take ios 14 and iPhone8 as examples, first open the settings in the iPhone, as shown in the following figure:

2. Turn on the sound on the settings page, as shown in the figure below:

3. After opening, click the ringtone in the page, as shown in the figure below:

4. After turning on the bell, find the default value in the page, as shown in the figure below:

5. Then you can choose the ringtone you want to change, as shown in the following figure: