When you start using Google Voice, the first thing you do is to claim one of Google Voice's freebie phone numbers. To do that, you submit a personal phone number as your "claim ticket". It sounds like you did that. So now you have an inbound Google Voice phone number, which is linked to your Frontier number as a forwarding number.
Your next step is to
port your Frontier number to Google Voice. Porting is a telco industry term for transferring control of a number from an old ("losing") carrier to a new ("gaining") carrier. This procedure will automatically cancel service with the losing carrier after the number's call routing is moved over to the gaining carrier.
But... you can't port in a land line number, since GV only accepts ports in from mobile carriers. SO, you'd have to first port the number into a cheap prepaid mobile carrier, wait a week, then port it to Google Voice.
See:
https://support.google.com/voice/answer/1065667#xferin