On 7/1/14 I encountered another situation where I was late (13 days) in refilling my minutes though the purchase of another pre-paid card. I was told at that time that AT&T has a 60 day grace period in which to re-fill minutes and have "expired" minutes reinstated. I then purchased a $100 refill card, had my expired minutes reinstated and left with a new balance of $100 plus my "expired" balance. AT&T HAS NEVER CONTACTED ME WITH ANY NOTICE THAT THIS POLICY HAS CHANGED!
AT&T targets their Go Phone plan to seniors, who only use a cell phone infrequently for travel or emergency calls such as a power outage. If someone's minutes card expires, they now pocket all of the unused minutes if you do not renew your service by buying another pre-paid card (in this case $538.50). If you do renew, they still pocket all unused minutes except $100 worth. This is a predatory and unscrupulous business practice.