A simple port request (1 phone number) has to be resolved within 24 hours, and complex port requests have similarly short SLAs.
The FCC has defined these SLAs and if you ever have a losing provider that is close to breaking the SLA on a port request, search for the providers local number portability escalation list and call each contact until resolved.
Prior to Voxbone joining Bandwidth.com they were a provider we had chosen to avoid.
Voxbeam and Anveo Direct are solid choices for international DIDs.
Bandwidth.com has a poor reputation FYI, they pissed off a few Public Utility Commissions and were blacklisted from getting new phone numbers in some states.