In which case, she needs to write to them formally, recorded delivery, stating what her insurance company say, and insisting that they pass the letter to their insurance company. This is the correct way to do it - her claim is against the garage, and they then refer it to their insurers, she wouldn't make the claim direct against the insurance company in the first instance. Say in the letter that she wants a written acknowledgement and that if she doesn't get it she will take legal advice. If she doesn't get a reply in fourteen days, follow it up.