My supervisor published our work without informing us. Can we retract the paper from the conference in anyway?
Disclaimer: IANAL.

As you evidently realized yourself, your supervisor had no right to do that. It is a completely unethical kind of behaviour which breaches academic rules to a great extent.

First, you must carefully weigh your options. In particular if you and your partner are still in this department and plan to stay there doing your PhD for example, be aware that your actions might have serious consequences for the people in this department (especially the supervisor obviously, who would face disciplinary sanctions), and they might resent you for that; it could damage your chances there. 

If you decide to proceed, I would suggest to contact an appropriate instance at the level of your institution (not your department, since it proved useless). I'm not sure which one is the most relevant: I would probably start with a students representative or union, otherwise ethics board or legal office. I'm assuming that they would support you and in the end force the supervisor to retract the paper.

If this doesn't work for any reason, you can raise the issue directly with the editor. IEEE is likely to take this kind of issue very seriously, they will check your evidence and probably ask the supervisor for explanations. If they are convinced the paper will be retracted. In this case the consequences are probably worse for the reputation of the supervisor, the department and the institution: this a public sanction by a renowned editor, as opposed to the official author asking themselves to retract it.