1. install Zoiper IAX SIP Voip Phone from app-store and launch it

2. Click on Settings then Accounts

Now click + button to add a new account and press yes

3. tap on Select Provider

4. Select UltraTone

5. Account Name: UltraTone

Domain: voip.gpnsystem.com:55061

Username: [Your GPN 6 digit number]

Password: [Your  password]

Caller ID: [Your GPN 6 digit number]

Auth Username: [Your GPN 6 digit number]

and then press Register

6. if you see the tick button it is connected and ready to make call.