iPhone 4 loses all Provider services for hours each day

I bought an iPhone4 outright from Koodo this past August 8, 2011 for my daughter who is in University.

On Thursday November 3rd she said the iPhone was losing all Koodo service.
We called Koodo Monday November 7th to see if they could help;

Service Guy suggested putting a new SIM Card in the phone. We did this to no avail and the iPhone still loses all Koodo Service for 4 to 12 hours almost every day.
What’s our next step?
The phone has been Ok other than this, the Battery is OK & she up graded to ISO5 when it came out. I just dont know whats going on?
Moe