If you're on campus you will need to talk to an International Student Adviser (ISA) before withdrawing. They will help you with the withdrawal process and refer you through to one of the Student Visa Services team members to talk about your visa.
International Student Advisers are available for drop-in appointments 11am–3pm in the AskOtago Central Hub
If you're not on campus, contact:
International Student Support
Student Visa Services