WhatsApp is blocked or slowed in some regions. A proxy solves it: messages and calls go through an address of another country. The app has an official Proxy setting.
For calls you need a stable proxy with low ping, otherwise voice stutters. SOCKS5 suits better than HTTP — it works with any traffic.
Take a proxy of a country where WhatsApp works fully. A live verified pool is a must — a dead address simply will not connect.
Setup takes a minute: address, port, and the app reconnects through the proxy.