Greetings Tinafan80,
Thank you for using Apple Support Communities. It seems like you receive text message notifications while on calls, but the volume of the notification sound is played as if you are not on a call.
If you lower the volume of the Ringer and Alerts, does the notification sound lower while on a call?
Are the notification sounds just as loud while on calls when using a different app?
- Go to Settings
> Sounds & Haptics (on supported models) or Sounds (other models). - Tap Text Tone, then do one of the following:
- Tap Vibration, then choose an option.
- Tap a sound below Alert Tones.
- Tap Tone Store to download an alert sound from the iTunes Store."
Change message notifications on iPhone
- "Go to Settings
> Sounds & Haptics (on supported models) or Sounds (on other iPhone models). - To set the volume for all sounds, drag the slider below Ringers and Alerts."
Change iPhone sounds and vibrations
Please don't hesitate to let us know if the steps resolved your issue or if you need additional assistance.
Take care.