Free Apple Developer accounts limit you to 3 active sideloaded applications at any given time. If you hit this limit, you must deactivate or delete an existing sideloaded app within AltStore before installing GBWhatsApp.
Many of these services require a paid "signing certificate" to prevent the app from being revoked by Apple. Jailbreaking ipa apps me gbwhatsapp install
If you tell me if you have a computer available, I can help you choose the best installation method (AltStore vs. Third-Party Store). Do you have a Mac or PC? Is your device jailbroken? Use Flekstore to Install GB WhatsApp on any iPhone Free Apple Developer accounts limit you to 3