Google Voice can only port in mobile numbers. Your Callcentric number is now a land line. So, you would need to first port it into a prepaid mobile phone carrier (GoPhone or T-Mobile work best), using either any old unlocked GSM phone and a SIM from the carrier, or the cheapest "burner phone" they sell.
Wait a week or so for the carrier database to get updated to reflect that it's now a mobile number, then port it into GV. Of course, if you don't want to do this, you are welcome to get a new number from GV.
Note: GoPhone accounts do not display the necessary account information to the customer. You need to contact GoPhone customer care, and specifically ask them "I need to port out my GoPhone number. What is the account number I need to use to authenticate my account during porting?" Your PIN is the PIN used to look at your account information on the GoPhone website.
See:
https://support.google.com/voice/answer/1065667