EssentialMED - Poor service and very unprofessional

My son went to the emergency at Linmed hospital. Firstly, phone Essential med to get pre-authorization and i was told someone will phone me back. After 30 minutes i had to phone again because no one phoned me, again I was told someone will phone me. I never received a call and obviously I can't wait because my son had an emergency. I paid everything that needed to get paid and the following couple of days send all proof of payments with invoices to Essentialmed claims department where I was told my proof of payment was not good enough and that they need to get invoices from the hospital (which I actually supp****). I had to wait another week before all this is done only to get short paid as to what I paid the hospital with no explanation or statement on how they calculated the refund (according to my plan everything I paid for is to be covered) No one is responding to me or contacting me back about this short payment. I am sick and tired for paying for a service and get treated like this. All I want is the short payment to be settled