In most cases, you can port a phone number to a VoIP service. This is recommended so that you don't have to give all your contacts a new number.
VoIP Phone Number Porting – Everything You Need to Know
You’ve been using a phone number for years and many people recognize you or your business by it, and you don’t want to give it up for a new number. Switching to VoIP means changing your phone provider and also your phone number. Can you still use your existing landline PSTN phone number with your new VoIP service? Will your VoIP provider allow you to keep your existing phone number?
In principle yes, you can take your existing number with you to the new VoIP (internet telephony) service. However, there are limitations.
This feature is not always free. Some VoIP companies offer number portability for a fee. The cost can be a one-time payment or a monthly fee, as long as you keep the ported number. So if you care about number portability, discuss it with your provider and factor the final cost into your cost planning.