Mero suggestion ma ta talk to them , come to a conclusion. Don't talk over the phone , always email. Tell them due to unforeseen circumstance you will have to leave. Or tell them the environment you are working is hostile and not workable.

If it's not a big pay raise I do not see the point of leaving them, ask them for a raise and tell them, you will need the raise.

Reply to the email stating, That they made you pay for the GC which is illegal and will work if they you pay back the amount you paid for the GC.

Always use email...no phone conversation. Do not admit anything, do not agree to anything or incite anything.