Don't let them get away.

You can ask HR the same questions. If getting no response, send another followup e-mail, stating that you send them an e-mail earlier and did not get an response so you try again. Let them feel that you are keeping a record of events ... hint of legal actions.

Generally there is a process of escalation. You gradually ask harder and harder questions, as hard as whether you should consult an employment lawyer since you are getting no answer from them. They will face the reality of legal risks.