I have a strained hamstring due to work, so I went to the doctor and they suggested me to take a week off and they gave me a note to give to my job. I went to my job, but they didn't believe it was work related. However, I didn't report it first to job before going to the doctor. I do not know since it's my first job. One of the shift leaders said "Well see if we can still hold your job?" I was wondering if they can fire/laid you off even if you have a doctor's note? Thank you.