Legal Question in Business Law in California

You should consult with an experienced trademark attorney who can advise you whether you have a valid claim. This is not something that can be determined in a public forum, since there is no clear-cut single answer.

I would recommend contacting a nearby attorney specializing in intellectual property or even general business, and start out by having him/her check for the other company's legal rights to its name (if any), e.g., have they registered it with the Secretary of State as their corporate name or filed for Federal trademark rights or something of this sort. It will be helpful to have a firm factual and legal basis before proceeding against the other company, including dates of use and any steps to establish and protect the names taken by both. Then, once armed with all the facts, I recommend starting off with a polite but firm letter from your lawyer, stating your case as strongly as the facts allow and making demands that are reasonable given your company's relative rights. Resort to a lawsuit only if the letter or letters don't produce results.