The answer may depend on your country's service providers and number portability from network to network they offer.
Usually, from my understanding of Skype, number portability is not offered, as Skype are allocated their own numbers to use for Skype Online Number service. So other phone service numbers cannot be used on Skype.
Depending on your business and the current numbers you have, maybe you could check with your phone provider about a voice message service that tells the caller your new

number and that this number is now changed?
I was lucky two years ago when Skype online numbers were introduced, I was able to get my Mobile Phone number and my Skype Online number to match the last four digits of my home landline number. I too, would have liked to have my home phone Telecom number transferred to become my Skype number, but it is not possible to Skype though I can change it from Telecom service to Vodafone or Telstra Clear networks.
Steve