No response after 3 weeks of emailing Bankmed

I emailed Bankmed on the 5th of November to get pre-authorisation for a procedure I need to go for but I get no feedback at all. I used email cause I included a scanned note from the doctor. I also prefer email as it is less easy to dispute. Since then, I sent a reminder 2 weeks ago and included almost every email address I could find on their site. I got autoresponses that my email has been received. Today again I have sent a reminder and again got autoresponses.