AT&T, following last year's embarrassing botched update that kicked every device off its wireless network and blocked over 92 million phone calls, is now promising full-day bill credits to mobile customers for future outages that last at least 60 minutes and meet certain other criteria. A similar promise is being made to fiber customers for unplanned outages lasting at least 20 minutes, but only if the customer uses an AT&T-provided gateway. The "AT&T Guarantee" announced today has caveats that can make it possible for a disruption to not be covered.