Yes, you can use your existing phone numbers with PureCloud Voice.
To do so, you will transfer your existing phone numbers into PureCloud Voice system using a procedure called Porting. PureCloud Voice provides an automated procedure for porting toll-free numbers - you just enter the numbers and follow the steps. However, porting DID numbers is a manual procedure performed by our support technicians - you submit the numbers in a spreadsheet along with an LOA (Letter of Authorization) form.
See the following articles in the Resource Center for more information on porting numbers into PureCloud Voice:
Port toll-free numbers
https://help.mypurecloud.com/articles/port-toll-free-numbers/
Port DID numbers
https://help.mypurecloud.com/articles/port-did-numbers/