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I am sorry to hear about your situation. Unfortunately, unless you can show that you're being discriminated based upon race, age, gender, or disability, you probably have no case against the church, and your rights would not be violate here.
Illinois is an "at will" employment state. At-will employment means that without a contract, you have no contractual or other right to employment with the company. The company is entitled to fire you for any reason: a good reason, a poor reason, or no reason at all--as long as the company does not fire you for an illegal reason (race, gender, age, religion, etc...). a But it extends beyond firing, to hiring, promotions, demotions, wage cuts and raises, disciplinary actions, and even scheduling. Unless you can show that this was done in violation of a contract, union agreement, or a clear violation of an unambiguous and binding clause against the employer, or that it was done because of some minority status (age, race, gender, religion, disability) that you have, then they do have this discretion. Now given that it's a church and the 1st amendment does give freedom of expression of religion, the church can even discriminate against you based on religion.
In short, they can do this, can require that you be there, etc... Whether or not you should, that's up to you, but if I were you I'd want some input into the matter.
I know this is probably not what you wanted to hear, but it is the law. I hope that clears things up anyway. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for my answer unless and until you rate it a 3, 4, 5 (good or better). Thank you, ***** ***** luck to you!