NEED AUTHORIZATION NUMBER

We have been requesting a pre-authorization number for a stent removal for over three months now. Affinity are saying it was a pre-existing condition, but they can check the dates and my husband was rushed to hospital when he was already on the plan. I don't think anyone knows when a kidney stone will form unless they can read the future. We called Affinity after the stent was placed and they confirmed that he would just have to wait a year until he could have it removed. So we continued to pay for the next year. Now, the year is up and they will not give him a pre-authorisation number. What is the problem? We would have cancelled a year ago if we knew this then. Pull up their records, there will be a recorded call. He is in a lot of pain and the stent needs to be removed asap. Please help