Provider changes

Hello, im new in the asterisk enviroment, but at least i know how to access the server remotely and change the .conf files.

My questions is this, my company currently has a service with Vonage, we want to change the settings so we can receive calls to a new number from outside.

Can you give me a hint what files are the ones i have to change? According to the new provider, i have to change some things at iax.conf file, but i dont know if i have to add more lines in other places. Thank you.