Alarms don’t go off

Hi, so I just slept through my class because my alarms did not go off. I had alarms set ten minutes apart starting at 7 am and my volume was up and my phone was not on silent. Sometimes the alarms do go off because I wake up to them but sometimes they don’t. I know my phone wasn’t on silent because what woke me up was a text message. This is kind of an issue and I used to rely on my phone for my alarms but now I’m scared to because this is not the first time this has happened but I usually catch myself and can still make it to class on time but today that did not happen. Is there a reason why alarms just do not go off sometimes? These are the same ones I set every Monday Wednesday Friday so they work most of the time but some days it’s as if no alarms were even set.