Mammogram

I have BCBS of TX. I had a mammogram last year on Dec 18, 2020. I try and do it every year around the same time to stay consistent. This year the 18th falls on a Saturday so I called and spoke with Jeremy at BCBS and he said I could get it a day early since it was a preventative appointment but when I set the appointment up with TOPS she sounded doubtful I could do it even a day early. Can you tell me if I can still have my appointment on the 17th of Dec please?