I am frustrated today. I don't have any idea what to do?

I work as a technical support executive for a big company. I am trying to improve my quality scores by religiously following the quality parameters and i am very concious of it. The reason i am following it is that i want to be good in whatever i do. I want to raise my performance. Frankly speaking i do not have the gift of gab and my soft skills are not that good to talk diplomatic and try deciving customers. If the customer asks me something which i don't have any idea i do fumble and lose my confidence and they can feel it. Simply i can say i can't lie and i get caught if i try to lie someone, so my scores are very good when i do have the knowledge of the stuff when i know what the customer is telling about but our quality dept. asks me to show confidence even if you donot have the knowledge of the product. I am not able to do that. I am frustrated. The customer gets over my head and he yells over me and i have to bear it. If possible IM me at n3r_raj@yahoo.com Thanks a lot.