Communicate With the Interior Designer - Interacting with a prospective office interior design company whose work appeals to you is a good way to finalise your choice. Don't refrain from talking to all those companies whose portfolios are interesting and attractive.
And while you contact them, also check out their response to your query and new business proposal. A good company will always pay attention to what you have in store and reply to your queries promptly with complete information which shows their interest in new projects. Try and stay away from those who do not take your query seriously and are not excited about a new client. Such companies are unlikely to concentrate on client satisfaction.