COBRA benefits not being paid even though premiums are paid in full?

Hi! I was hoping someone might be able to give me some ideas on how to deal more effectively with my COBRA benefits administrator. My group health insurance through my employer was terminated 4/01/11 when I went down to part time status. I received my election form for COBRA benefits on 4/15/11 and mailed the form, along with payment for April and May on 5/02/11. The company acknowledges receiving this payment as of 5/10/11. However, I noticed on 5/16/11 that my prescription claims were being rejected. I logged on to the benefits administrator's website and found that my premiums were listed as being $40 higher than those listed on my election form. They were also showing an unpaid balance of $276 for May, even though the amount of my check was listed correctly (so even if their premium information was correct, I would only owe $80 more for two months, not $276). I immediately called to point out their mistake, and I was able to go online and see that it was corrected in their system the same day. However, two days later, my pharmacy was still being told that my insurance benefits ended 4/30/11, so I called the benefits administrator back to ask how long it would take before claims would be paid. I was told that they would continue to look into it and call me back by the end of business (last Wed), but that worst case scenario, the insurance company was not informed of my payment on Monday and it would take 24-72 hours for everything to be cleared up. No one ever called me back, and as of late afternoon on 5/23/11, claims are still not being paid. I called again today and left a message, but have not received a call back. I am getting very frustrated, as I paid my premiums 3 weeks ago and need to fill a rather expensive prescription. Based on my experience thus far with these people, I also don't trust them to make sure I am reimbursed if I go ahead and pay out of pocket. Does anyone have any advice on my legal rights, or things I can do or say to get this useless company to handle the issue promptly?