What happens if your VOIP company just closes one day?

This is more a hypothetical but has happened and bound to happe again

You're a normal residential customer and you have an old landline voip number ported to a voip provider.

One day you wake up and find the phone no longer works and then find out they have shutdown/gone brankrupt/etc.

What would you have to do to try and get your number back? I know there is a 30 day period and it will probably go back to the original block phone number. But who would you contact to try and reclaim it?

In reply to a post by frogger2600:

But who would you contact to try and reclaim it?

Same as if a provider on a fixed line disappeared; try any new company see if they can reclaim, or contact Ofcom.

If the number was a BT number they might also have a record.

You could ask a provider to do an ORDI (Openreach Data Integrity) check.