​Landlord sold office plaza and didn’t tell us. (IL)

UPDATE: Thank you very much for the help some of you provided. I thought it was okay to ask this here because we own a small business and that didn’t sit well with some of y’all. – We do not feel we are “owed” anything, we were just looking for advice. We were caught off guard by the whole thing. For those that downvoted me into oblivion…🤷🏻‍♀️ – We will be contacting our attorney and we have canceled the ACH.

A lady approached our door one day and said we had to pay rent to her office because they are the new owners. We took the paper and said we would look into it. We received another letter (just dropped in the mailbox, not via USPS) saying we have to pay by ACH. We have not received any proof of anything, the old landlord is not returning our calls, and now the “new” company is asking US for a copy of our lease. We do not want to default however, we don’t know how to pay the rent. Any advice?