Looking at the first you linked to:
https://www.ivaadvice.org.uk/
They are run by Guardian Insolvency, who do have an IP registered with the Insolvency Service, who is also a member of an authorising body, The IPA. So looks genuine.
The second one ... which is the one I found ...
https://www.iva-advice.co/
These look like packagers -- which many IPs use as lead generators and information collectors. They do not have their own IP but pass details on to various firms on their panel.
The Debt Resolution Forum is a trade body for Insolvency Professionals --- Not sure how or why they would be passing your number on to anybody --- or why they would have it in the first place.
Sounds very much like a fishing exercise.
You ask "What is IVA doing to shut down these scammers!?" .... Are you referring to us here ? We are not a regulatory body, but a forum of people who have been in an IVA with a spattering of experts willing to give support.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014