The attorney is being cautious in not wanting to speak with you in case you have an attorney. Your initial communication may have indicated that you had retained counsel, and we have rules about speaking with someone that we know is represented by an attorney. Not a good idea. See RPC 4.2.
There is nothing to prohibit you from writing to the attorney for the health care center and explaining that you believe there is an error in the amount of the center's creditor's claim. If they filed a creditor's claim properly, then you accept it, reject it or accept for a lesser amount in the time allowed. None of this really requires you to speak with the health care center's attorney.
Alternatively you can hire counsel to be sure that the estate or some part of the process is handled correctly. Hope this helps. Elizabeth Powell