Advice on how to connect to a human on the phone

I am from a provider office. I have been trying unsuccessfully to reach a human being regarding claims from December not being paid/or acknowledged. I do not understand how I can not talk to a human being. I have tried every way on the phone and even sent email to provider rep - all to no avail. Please let me know how a provider can talk to a person and what can I do to get a human to talk to me?