Before you do anything, remember the following:

1. Wikipedia pages are fluid and can change many times a day.
2. Wikipedia does not have a policy about how firms can participate.
3. Page vandalism is to be expected for short periods of time. 
4. There is no single "webmaster" that you can contact. 

Make sure you read the detailed policies of Wikipedia. I recommend these two links as starting points: The Five Pillars and List of Policies. 

If you find something objectionable or inaccurate on Wikipedia, you can do one of the following:

1. You can participate in the forums related to the page and voice your concern. 
2. You can contact one of the previous editors of the page. 
3. Wikipedia does not condone copyright violations or libel. If you notice serious violations, you can contact Wikipedia at info-en-q@wikimedia.org.  
4. If Wikipedia does not respond to your emails, you can consider a press release or something low key. 
5. Do not simply go in and do massive deletions. If you are detected, the negative PR will not be worth it.