Dear Kiran,
One way of doing an attribute G&R is as follows: Choose about 20-40 calls. The quality analyst rates these calls. The response of the quality analyst can be used as the standard. Give the same calls to the quality agents (2 or more) for them to rate. This would be trial 1. After a few days ask the same quality agents to rate the same set of calls (trial 2).
The quality agents response would be used to check the repeatability and reproducibility. It is similar to call calibration, however, the objective here is to validate the existing measurement system. If the MSA is acceptable, then you can continue with your analysis. Else, you would have to fix the measurement system before any meaningful analysis.
Hope this is useful.