Changing My Job Hours?

I called out of my 8.5-hour shift today via the time app. I had previously notified HR and updated my availability to 6am-11am, Monday through Sunday. However, they scheduled me for three consecutive days from 10am-5:00 pm during my last week leading up to Christmas. Given my weight, age, and kids' school schedule, I can only work 4-5 hours a day. Will they accommodate my needs or let me go before my last shift on December 23? As a seasonal hire, I regret calling out and hope they will rework my schedule. If not, am I required to return my vest and name tag? I really hate myself for letting my family,target, and everyone else down. I was good on my 6am-10am shifts any day they scheduled me. It was just the 8 hour three days in a row where I could barely walk out to my ride,go from the car to the house door, and soaking in hot water. Just staying in bed all day recovering before my next shift.