Maybe weird hardware, but easily available on aliexpress. Y’all need to explore more. Appears to be scrubbed off now but used to be more available.

Tbh, contraptions like this have a long history for gray-market VoIP call termination, but usually in countries where governments charge a lot for incoming international calls as means of fund-raising (or inefficient telecoms) but domestic rates are low.

Merge with https://news.ycombinator.com/item?id=45353925 ?