Attempt resolution using other options first, such as:
Performance problem resolution
Influence without authority
Negotiating project changes
If the problem persists even after your team’s best efforts, document a summary of the problem. Include the results of all of your attempts to deal with it.
Outline possible approaches for solution that might be available to others with more authority, including any that you may not necessarily favor. Quantify the costs and other consequences of these alternatives as thoroughly as you are able. Also quantify any consequences of failing to resolve the problem promptly.
Provide the data to your sponsor or some other appropriate decision maker ...