Go to USCIS.gov and the "Ask Emma" chat box should be at the upper right-hand corner. Try saying "I-130" first, and it should bring you to that page. Once you are on that page say "representative". Then click within the chat window where it says "Case Status" and following that click where it says "Connect to Live Chat." Then enter your receipt number, which is taken from the I-797C Notice of Action letter. Then ask which service center is processing your case currently / where it has been transferred.
The last two times I have tried it there have not been any representatives available. But if you keep trying eventually you will get through.