Seeking advice re problematic DID port-in-progress

Hi, folks,

After declining to sign a new 2-year $500/mo contract with my formerly-favorite inbound VOIP (DID) provider - a wholesaler based in Brussels - I'm completing the process of porting the last of my DIDs from them off to other providers with lower minimum purchase commitments.

The first few dozen went smoothly, with no interruption in service (not counting the ~day of downtime that the Belgian provider put me through as part of their hardball contract negotiation tactics). However, the third-to-last DID has been in limbo for the last 3 days.

Right after my new Toronto-based provider reported receiving a FOC date (25 May) for this DID, the DID in question disappeared from my control panel at the Belgian company, and calls to the DID consistently fail from various calling providers. The CDR reports at both provider control panels show no calls (neither successful nor unsuccessful) for the DID in question.

When asked about this, the Belgian provider claims that they've been told by "a telco" (they would not name it) that the DID in question has been ported, which is (they claim) why the DID disappeared from my control panel. However, at least a dozen of the DIDs that I ported more than a month ago still show up in this control panel, even though I've confirmed repeatedly that all calls have been routing to the new provider since the port date. Additionally, my new Toronto-based provider (who have been fairly reliable) is certain that none of these calls are arriving at their network, which doesn't surprise them given the FOC of 25th May. Given these facts, and the way the Belgian provider has acted in the course of this contract negotiation, I think I'm being jerked around.

The end-user of the DID in question would dearly like for their inbound calls to work again - ideally well before the 25th. I really don't want my next step to be an FCC complaint (I'm based in the US), but I'm not sure what my other options are.

Any suggestions?

Apologies in advance - and suggestions of better fora welcomed - if this isn't sufficiently on-topic.