If you're talking about flip phones and trying to protect against an eavesdropper of a phone call or SMS, then there's no point. The network that these phones

If you're talking about flip phones and trying to protect against an eavesdropper of a phone call or SMS, then there's no point. The network that these phones used is full of holes already https://en.wikipedia.org/wiki/Signalling_System_No._7#Protocol_security_vulnerabilities https://en.wikipedia.org/wiki/Signalling_System_No._7#Protoc...