WhatsApp's End to End Encryption
You can easily secure messages with end-to-end encryption using the well known message app WhatsApp.
Simply click on the Chats icon, tap the pen & pad icon and select the contact for your friend and/or colleague. When you're then in draft mode to send a new message, tap on the person's name at the top of the screen. Scroll down and you'll find an option for 'Encryption' with a blue lock icon.
You'll be presented with the option to either 'Verify Security Code' or 'Scan Code'. Your contact will need to be with you when the end to end encryption is set up. Either they will scan the QR code on your phone, or you can use the scanner built into WhatsApp to scan the QR code on their phone. A 60 digit code is displayed that you can compare to what is shown on the contact's phone.
End to end encryption works by providing encryption keys only to communicating parties. In theory it should prevent a telecom provider from being able to decrypt the messages.