Hoping someone can help or has experienced a similar problem. We keep getting denials from MNBCBS for 64635 and 64636. These are done bilaterally and we have tried billing 64635-50, 64636-50 x 3. 64635-50 and then the 64636-50 billed with 1 unit per line x 3 and the denial we have been getting is CO 16 remark code N657 this should be billed with the appropriate code for these services........ these are the correct CPT codes and it seems no matter how we submit them they deny them. Anyone else have a problem with these or any suggestions? I have called the insurance company and all they will tell me is they can't tell me how to code. They are not following CPT guidelines, so I'm not sure what it is they are looking for. Appreciate any help!