A great sore throat cure is Cepacol Lozenges, sold at most drugstores and used in most hospitals. As far as cough and congestion you should ask a pharmacist or doctor, as not everything is right for everyone.
The best cure for sore throat is Manuka Honey. It is honey made from Manuka bush found in Australia and NZ. It was recommended by a doctor and even works on viral infections. The most effective cure that me and my friends have come across.