It's regarded as acceptable etiquette only to contact a client (or their company) directly if they approached you first. If your voice is the one they've decided to work with, they will contact you.
Frequently, a listed company or brand is not directly involved in the project, as they're often handled by advertising or marketing firms. Any unsolicited contact might confuse or upset representatives of the company and possibly harm either Voice123's, or the client's, reputation.
A client's time and privacy should be respected. The consequences of disrespectful conduct brought to the attention of Voice123's Customer Success team may include the cancellation of a membership without refund, as well as a ban from participation in the Voice123 marketplace.
Legal Note: You are responsible for conducting your own investigation regarding any and all claims made by prospective talents, agents, or clients.