"Mobile state disconnected" sounds like the result rather than the cause.
Unfortunately "it doesn't work" doesn't give us much to work with, and since you don't tell us what ways you have tried to solve it it's likely we'll just end up suggesting things you've already tried.
So, just to clarify, this is just mobile (cellular) data and WiFi still works, and you still have phone (voice, SMS) connections? Have you checked the trivial things like whether your APN settings are correct, that mobile data hasn't just been turned off? Spoken to your service provider to check that there isn't a problem with your account, or a service outage where you are? The more you can tell us the more chance we will be able to suggest a solution.
One other thought: have you tried your SIM in another phone, or another SIM in your phone? That will tell us whether the problem is with the phone or its settings or with the SIM/account/network.