incoming message alerts

Hello angelnut,

These steps found at Change message notifications on iPhone - Apple Support should allow you to choose the sound for incoming messages:

Set the alert sound for message notifications

1. Go to Settings  > Sounds & Haptics (on supported models) or Sounds (other models).

2. 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.

See Change iPhone sounds and vibrations.

There is also information on how to assign a unique sound for a particular contact.

Have a great day.