It does in the privacy settings allow you to limit it to premium users and contacts, but in my experience old people flat out refuse to alter their settings, or in general follow any security related instructions. If you can get physical access to their device and make them do it, sure.
Telegram FOSS perhaps?
Doesn’t prevent scammers from contacting his father
Telegram doesnt have block call and sms from unknown number?
It does in the privacy settings allow you to limit it to premium users and contacts, but in my experience old people flat out refuse to alter their settings, or in general follow any security related instructions. If you can get physical access to their device and make them do it, sure.