If you're an extroverted type of person (and many salespeople are), but your employees are introverted types, you may make the mistake of thinking that they are capable of adapting their behavior to fit your extroverted behavioral style. They can't.
If your goal is to communicate with, lead and motivate others, it is incumbent upon you, the extrovert, to adapt to others' introverted style of communication. If you don't make this adjustment in your approach, you run the risk of appearing patriarchal and arrogant, and the introvert will simply shut down. The harder you push, the less likely the introvert is to respond to an extroverted style of communication.
What your employees need is a leader who can catch them doing things right and compliment them. Praise the way they answer the phone or prepare a file, for example.
The way to improve employees' performance is to let them know in advance that you are planning to have a review meeting with them in the not-too-distant future (10 days to two weeks). Let them know that you want to talk about what's working and what needs improvement and that you would like to have their input.