Prepaid calling card

I am a retired military spouse. My family lives on Guam. I wanted make sure my mother didnt have to pay to call me, so I got her a calling card. She recently is having problems using the card. It still has mins on it & is no where near expiring. I tried every number I could find & all I get is automated voice response. I feel like I am getting ripped off. Please help to to get to the proper channels. Thank you