Download app from App Store here: https://apps.apple.com/us/app/linphone/id360065638
After installation start the app.
You might be prompted by iOS to allow access to your address book and microphone. Please allow.
You now can see an unconfigured softphone running with dial pad.
The indicator shows that it is not connected to a VOIP provider.
Tap menu button and select "Assistant" option.
Select "USE SIP ACCOUNT"
Enter your "SIP account ID" in the Username field.
Enter Password for your "SIP account ID" in the Password field.
Enter your sip server address for your "SIP account ID" in the Domain field.
Select UDP for transport type.
These credentials above can be obtained at Equipment tab via KOMPaaS Portal.
Below an example of successful account setup, although you need to check few things there.
Click on the account and check the following settings:
Tap on Settings menu:
Navigate to "Audio"
Enable only these two audio codecs below, as only they are the supported ones.
Navigate back and select "Network" settings and set the settings as shown below:
Navigate back to dial pad, you should see "Connected" status.
The configuration is done.