There isn't a tutorial showing how to do what you want and what you want to do is complicated. Your Project requires several skills. What have you tried?
This stuff might help .
- Use a Speech Recognizer to command an activity. What is discussed could help you make a phone call using the SpeechRecognizer if you already know the number. Using Contacts is probably much more complex.
- This tutorial might help HOW TO: Program the native SpeechRecognizer for Continuous Dictation and to do things . It shows how to get the SpeechRecognizer to recognize voice commands and use it to do things.
- How to access the phone numbers in your Contacts seems to be discussed in How do I get contact list in App Inventor