Besides making calls from the phone dialer screen on HTC ChaCha, you can tap a number in a text message or email to call, or press a single number on the keypad to quickly call a contact.
Note: Most SIM cards come with a PIN (personal identification number) set by your mobile operator. If you’re asked for a PIN, enter it and then tap OK. If you enter the wrong PIN three times, your SIM card is blocked. Don't worry. Just contact your mobile operator and ask for the PUK (PIN Unblocking Key).