Be sure to use sick time for each call off as that is your protected time off, meaning you shouldn’t receive corrective action until you reach a point where you’re out of sick time. As a caveat since it’s a chronic condition, it probably wouldn’t hurt to call PRSC to see if you need to seek a workplace accommodation as well

technically they CAN fire you, most places have a policy about how many call outs until it’s a verbal warning, then write up, then termination. with IBS it’s harder to accommodate because it’s much more than just needing a chair at register, because either way with calling out or the accommodations you won’t be on the floor. id take some time to think about what accommodations can help you, like if running back and forth on bar will make it worse/any tasks that would make it worse, make a list of things you think will help and hopefully being open with your manager will make it go easier

It’s likely that you will need to submit paperwork for an accommodation. If you don’t you are still subject to the attendance rules even if it’s a good reason and can get let go.