The following Master’s Thesis examines the role of service designers within the AI Voice Assistant development process. The author is researching how service designers could use a human-centred approach and limit the gender bias presented by voice assistants while stimulating AI voice assistants usage. The thesis is navigating through the problem within Service Design thinking and uses the Double Diamond design approach. The project starts with an initial problem formulation, which is later adjusted in accordance to user needs and design ethics. Service Design methods such as actor map, system map, user journey, persona, empathy map, blueprint help to address the problem with complexity, namely to get to use the service through the service’s touchpoint - the voice assistant and secondly having seamless experience for users across the touchpoints. Focus of this thesis is primarily on Service Designers that will benefit from the new tool that describes how to work with non-human actors in service design while using a persona method for a non-human actor. The author came up with a design tool for Service Designers to implement into their project work. The tool for voice assistants' personalities limits gender bias but allows users to customize voice assistants. The thesis provides examples of voice assistants personalities and conversation use cases that are depicting the conversation flow and tone of voice of these assistants. The different voice assistant’s personas and conversation use cases were tested with users. Then the persona profiles were evaluated and finally the persona tool was adjusted based on the expert’s feedback. The provided Persona tool for virtual voice assistants might serve for service designers as an inspiration or a tool for developing personalities for digital voice assistants as non-human actors in different contexts.