I tried when a had Health Net. I could not get it done. I would think I was close and then they would send me somewhere else. They wanted me to loose 30 pounds before surgery and I came close, but I could not do it.
After two years of thinking my surgery was just around the corner I switched to Kaiser. Two people at work had and one had surgery, the other a date. I went to the information class, the 12 weeks of prep classes, and had surgery 11 months after the switch. It was great and the classes made me well prepared.
Don't give up, you are already doing well. Document your success and keep pushing them.