who do you contact in Virginia,when an employer will not pay commissions to an independent contractor?

Answer 1

What are the terms of the client/ Independent contractor agreement?

If it provides for payment of commission and the client has failed to respect his/her commitment, then a breach of contract may have occurred. If that is the situation then attempt to collect at Small Claims Court, or if you want to pursue a bigger case contact a competent Employment Lawyer (call the local Bar Association for referrals).