Unit of Issue problem

Hello,

I am facing a problem in unit iof issue.

I need to change the Unit of Issue in SAP material master. When i tried to change that then got error as mentioned below:

The unit of issue cannot be changed because the material is used in a BOM
Message no. M3214

Diagnosis
The unit of issue can be changed only in the following cases:

If there is no change in the dimension of the unit of issue, and if the unit of issue is not dimensionless

If the base unit of measure and the previous unit of issue have the same dimension, and are not dimensionless

Now even when we tried to change this in BOM then also we got the same message. We do have change number active in CS02.

How to change this .. what are pre requisite.?

Regards

Himanshu