If you have active Aircall numbers and want to port them to Ring4, you can request a phone number transfer to Aircall.
1- Here is the Aircall for the port-out: https://help.aircall.io/en/articles/3819517-porting-away-your-aircall-numbers
2- Create a Ring4 Business account: go to www.ring4.com and open the console
3- Request the port-in of the number: Fill the Ring4 porting form
The porting process can be immediate or last up to 2-5 business days.
To learn more about Ring4, visit www.ring4.com