First of all, invite the company by using the invite company option to your thread. And if you are unable to locate the option then this thread "Tutorial: How to Invite a company to your thread." will help you to find out.
Note: Invitation button will be enabled when your first post reaches 4 days old.
Note 2: Make sure to follow the suggestions correctly, when you do it correctly you will get below message in your thread automatically.
Note 3: Make sure to share your account number (Only account number). Many time this help companies to find out you are genuine or not.