For higher-scale origination,
AnveoDirect has an API to buy voxbone DIDs anywhere in the world. (Voxbone has a stellar reputation.)
If you just need a few 2-channels DIDs you can use
localphone (this is
my link), they resell voxbone for most routes.
For competitive international termination, I usually use
voxbeam's premium route and
net2phone's as a backup.
Anveo, voxbeam, net2phone have a pre-payment of $50-$100. Other carriers include siproutes, alcazar, and xconnect but they require manual setup and/or possible large minimums.