People will rarely change their mind about something right away. You have to SELL them on the idea of it. Sometimes you’ll have to go over the same topic time and time again to get them to see things from your side.
Try to ask them questions about WHY they feel that way and use that information to go back and get them to see why your product/service/idea is better. If you can tie your pitch back to something you just found out about by asking a question, even better!