Subnet being blocked by Level3 due to prior owner's misuse

[brock at bmwl.co (Brock Tice)]

We have a subnet that used to belong to someone else. One of our
business customers that was recently moved to that subnet is being
blocked from accessing one of their supplier's web site that's hosted by
Level3.

Our attempts to work through the supplier to resolve the issue have not
worked as they are not aware of what's happening at that level. Our
other attempts to resolve this have not worked.

Would someone from Level3 be able to help resolve this off-list, or does
someone have the appropriate contact information?

Thanks,
  --Brock