You can start by being honest. Listen to problem and stop trying to sell products.
Provide real resources and solutions instead of trying to sell products on the help line. Help means that you provide the service asked for, or you are not helping. You add insult to injury when you do not listen, get upset or tell your customer that they are wasting your time, when they are asking for help and you are selling unnecessary products for a simple solution. "Change my Password" access information. The information on file is obsolete. I have new information. Getting mad hanging up and insulting customers will loose you business.
I agree products should not be sold on the help line. the customer should receive the help asked for.