Stop thinking about you and focus on your customer.
What do they want? How can you help with it? Try and profile them a bit, and adapt your speech in away they will most likely find appealing.
It's not about being social or funny, it's about being social and funny to that specific person with a goal in mind. If you have one product, there are so many scenarios you can be presented with you have not already seen before.
Based on your interactions with people, you could try and start making decision trees to help you navigate conversion flow. It might help you feel more confident.
If you really can't talk, then you should consider a different carrer.