Human-Robot-Interaction (HRI) research is typically built around the premise that the robot serves to assist a human in achieving a human-led goal or shared task. However, there are many circumstances during HRI in which a robot may need the assistance of a human in shared tasks or to achieve goals. We use the ROBO-GUIDE model as a case study, and insights from social psychology, to examine how a robot's personality can impact on user cooperation. A study of 364 participants indicates that individuals may prefer to use likable social robots ahead of those designed to appear more capable; this outcome reflects known social decisions in human interpersonal relationships. This work further demonstrates the value of social psychology in developing social robots and exploring HRI.