If they won't return your calls, maybe they'll return your lawyer's call -- or, more likely, answer his letter.  I don't think you have any other choice if you want to pursue this, but to hire an attorney.You might have a moderately severe injury.  The real question in this case will be whether the store was negligent (carelessness meeting the legal standard), and how much of the carelessness was yours, if you stepped in a puddle on the floor without watching where you were going.