Dr stopped process of implantation

I've been going thru the process of IVF and I was supposed to have the implant on Tuesday tomorrow, but last Thru when I went for a sono, the Dr asked me for $4500.00 for the thawing process. I was in shocked and told him my insurance covers for it, he said they dont. I asked him if he checked he said no, but there was another patient that had the same insurance and they didnt pay for this process. I told him insurance are different. I called my nurse provided by the bank i worked with, she assured me and read my benefits and said I'm covered. This doctor is a money hungry Doctor, I had to pay for everything up front, now I'm going with a different doctor. Can something be done for this? He stopped the process because I didnt give him the money and he said he preferred cash.