Voice over IP (VoIP) has gained widespread acceptance and is used for many business communications already. However, voice calls in traditional phone services, as well as in VoIP systems, have some security flaws and therefore can be easily intercepted, which can cause high damage by, e.g., industrial espionage. To establish secure and private phone calls, additional non-invasive measures are required to protect the signaling and voice channel between the parties for existing and well known VoIP applications. We propose an approach for secure and privacy sensitive VoIP communication by introducing an additional security layer. The introduced security layer can be applied to known VoIP solutions on different channels (e.g., soft phones or mobile phones) and is independent from the deployed VoIP implementation in order to improve security and privacy of VoIP calls for company systems.