Are you in control of the Yahoo listings? If so, you would've been notified when such drastic changes took places on them. If you didn't claim them, then it is possible someone else did and changed the information. The listings places are getting better about verification methods, but it's still possible for competitors to claim unverified listings.
I would suggest creating a Yahoo Small Business account, and then contacting Yahoo about the situation. They should either give you ownership, change the URL, or delete the listing and have you create a new one. If Yahoo is being too slow, create a new listing in the meantime, and once you get in contact with Yahoo they should be able to merge the two listings.
Yahoo is the slowest of the three in getting back to you (in my experience), so don't be afraid to get a little aggressive if it starts taking a while. Contact them through multiple channels, flag the listing, etc.
I have seen competitors take over listings in the real estate market before, and the insurance industry would seem like another clear target, since the business/agent structure can be similar.