A no call no show is a fireable offense the first time it happens if that's what you're talking about. The only reason it would be excused is if you had a genuine emergency that prevented you from contacting the store before your shift. For example, one of my coworkers no call no showed but it turned out she was in the hospital so it was excused.

If you're talking about normal call outs, I'm not sure if there is an official policy on how many you can have.

Sick time can be used for unexcused absences, but if you have no sick time, then any instance of missing your shift can be written up for disciplinary actions—and after one time, you can be fired for any further offense