Use Transaction ME52N. Check to see if the PR has already had a PO issued against it. If so, you must inform the Purchasing Group. Check if the PR has been approved. If so, you may only make changes to a limited extent and may be subject of approval. Check if the PR was created by MRP. In this case, you don’t have much control over the modification process.
All changes to items are logged and stored. Information stored includes when the information was changed, who changed it, what the changes were, etc. Select the desired item in the item overview and choose Go To –> Statistics –> Changes.