Text/reminder sound alerts

Hi MrG029,

Welcome to the Apple Community.

Apple support have articles available online (links below) that may help.

You might want to select just a few, or check them all out.

How to put your iPhone on vibrate, ring, or silent mode

(ie: Make sure iPhone is not in silent mode)

https://support.apple.com/en-us/HT208353

Use Reminders on your iPhone, iPad, or iPod touch

https://support.apple.com/en-us/HT205890

Change iPhone sounds and vibrations

Tip: If you’re not receiving incoming calls and alerts when you expect them, open Control Center,

then check whether Do Not Disturb is on. If  is highlighted, tap it to turn off Do Not Disturb.

(When Do Not Disturb is on,  also appears in the status bar.)

More in the complete article: https://support.apple.com/en-au/guide/iphone/iph07c867f28/ios

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Select (or change) ringtones and vibrations on iPhone

https://support.apple.com/en-au/guide/iphone/iph37c04838/ios

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Use notifications on your iPhone, iPad, and iPod touch

https://support.apple.com/en-us/HT201925

View and respond to notifications on iPhone

https://support.apple.com/en-au/guide/iphone/iph6534c01bc/ios

Change message notifications on iPhone

In Settings, you can set up and manage message notifications for the Messages app

https://support.apple.com/en-au/guide/iphone/iph62faab6a4/ios

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Edit contacts on iPhone .... (Eg Add ringtones for callers if you wish)

Tap a Contact, then tap edit

Allow calls or texts from a contact to override Do Not Disturb: 

Tap Ringtone or Text Tone, then turn on Emergency Bypass.

https://support.apple.com/en-au/guide/iphone/iph89a9c71d8/ios

Announce calls, messages, and more with Siri on iPhone

(Incuding notifications from apps like Messages, Reminders)

https://support.apple.com/en-au/guide/iphone/iph838fd6fd4/ios

All the best :-)