Pre-Authorization No not working After Hours

I made a review about a rejected claim in February 2021, they promised to resolve the case, they requested the clinical report from the hospital and there after still rejected the claim due to no pre-authorization. I would to express my disappointment with the poor service Unity health emergency. There is an emergency number provided on the Elixi membership card ***, when you call this number at night you receive a voice prompt that say their office hours close at 17:00 pm and refer you to the ER24. I had an emergency on 1 July 2020 due to Corvid 19 complications, called number and ended up being collected by ER24 to hospital. Now Unity Health has rejected my claim due to no pre-authorization, when I tell them that I tried to obtain authorization on the above number, they are claiming that the do have a 24 hour line which I should have seen on the policy documents(not on the card). I went through the documents, they only tell me about the requirement to obtain pre-authorization but not alternative number is provided. can someone from Unity health explain to me how exactly must we obtain pre-authorization, the provided number is not working after hours?