Contact one of the confidential advisers for academic integrity and ask to discuss the matter. They can advise you, mediate between you and other parties and help you decide whether or not you wish to submit a complaint. The confidential advisers will never take any action without discussing this with you first and getting your consent.
If your issue has not been resolved after talking to the confidential adviser, you can submit a complaint to the Academic Integrity Committee. The confidential adviser may help you prepare the complaint. The committee will investigate whether the complaint can be taken into consideration. They will issue a decision on this within three weeks of receiving the complaint. If the committee decides the complaint can be taken into consideration, it will start its investigation.