In the context of Network Functions Virtualization (NFV), telecommunication systems are more and more deployed on the cloud, using orchestration engines such as OpenStack Heat. Heat takes as input templates that describe the components of the target system and automatically performs the deployment. This prevents consumers of cloud services from handling the challenges of manual deployment. However, deploying such systems remains challenging. Indeed, the templates given to Heat may contain errors that can lead to a failed or a partial deployment, thus compromising the systems reliability. To handle this challenge, we propose a formal approach and a tool for the verification of templates consistency prior to launching their deployment. A case study is presented to validate the approach.