VoIP Phones - zoiper

You can download a part-configured Zoipier from here: Configuration instructions for Android and iOS

You can purchase Zoiper here: https://www.zoiper.com/en/shop/buy/zoiper5

If asked about MWI, you can select Disable.

Below is a sample configuration on an iPhone.

1. Download App and go to Settings->Accounts & select 'Yes'

2. Click 'Select a provider'

3. Select 'AAISP'

4. Configure the VoIP credentials from your VoIP number's control page.

5. Click 'Register'