Error 5B1: trying to call Italy

[SPCausi]

I have a subscription via my phone number xxxxxxxxxxxxxxxxx for international minutes.  
when I call my mother in Italy, I receive error 5B1. How can I fix this?

[slusagm]

how you call Italy?

the leading 0 could be an issue

To call Italy from Canada, dial 011 (Canada's international access code), then 39 (Italy's country code), and finally the Italian phone number, including the leading '0', which is part of the area code and required for international calls to Italy.