Tell them you said in the interview, you cant work, and that you WONT be turning up again on a sunday. and they can lump it
Do you have the days you're available to work on your job application from back whenever? Tell them that while you've been able to make the occasional exception, it can't continue.
You mention the fact that you haven't been to church in 3 months, and not all those were due to work shifts. If you voluntarily didn't go to work when you weren't given shifts what chance do you think you stand if you use as an argument for not doing your job? Quite honestly you either need to go to church every week or stop complaining that your being scheduled into working.
