You should retain an attorney to assist you at this point.
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USCIS's multiple explanations and answers is one of the best reasons you should be working with a lawyer. The interview can be postponed. There is a process to follow to get that done. Problems regularly occur and you are going to struggle greatly without a lawyer.
Traveling outside the country while you have a pending I-485 could constitute abandonment of your application for adjustment of status. You should have consulted with an attorney before scheduling this trip. Moreover, you should not seek to get legal advice from the USCIS customer service officers, as they are not attorneys and are not authorized to dispense legal advice. I agree with my colleague; you need to hire an immigration attorney immediately, before you make any further mistakes that jeopardize your green card application.
Answers provided by Ksenia Maiorova, Esq. on Avvo.com are of a general nature and do not constitute legal advice.