Porting cellphone number without consent

My cellphone number was ported without my consent. I am a telkom client and have been using a prepaid number for 10 years. I received a call to confirm if this is my number from Mtn I confirmed that this is my number but they still went and ported my number. I can loose alot of money because of this and this is how people bank account get hacked. I need this to be fixed by mtn and how do they port my cellphone number without my consent