Will it slow my phone or internet?

No. The tunnel carries WhatsApp traffic only; everything else goes directly.

Can you read my messages or calls?

No. WhatsApp encrypts them end to end before they reach us and we do not log your activity.

A random device identifier, your trial or plan status, your IP address while connected, and the payment reference. No name, number or email.

The installer is downloaded straight from the official site, takes about a minute and works on Android 7 and newer.

Download whats-call.apk from the home page. If a warning says the file may harm your device, choose “Download anyway”: it appears for every installer file.
Open the file from the download notification or the Files app.
Allow installs from this source (once) for the browser you used, then go back.
Tap Install. If Google Play Protect warns, tap “More details” then “Install anyway”. It appears because the app is not in the store yet.
Open the app, read and accept the disclosure, tap the power button and allow the VPN permission.
Fully close WhatsApp, open it again and test a call.

“App not installed”: delete any earlier Whats Call and install the new file.
Cannot find the allow option: Settings → Apps (or Security) → “Install unknown apps” → choose your browser.
The call does not connect: check it says Connected, then force-stop WhatsApp and open it again.

Download the file from the official site only, never from other links or groups.