FAILURE TO LOCK A LINE

I need to express my unhappiness in the failure of a call centre agent to carry out instruction to lock a line. On Monday night, 30 November 2015 I called Vodacom Customer Care to lock my data line. I have misplaced my 3G USB modem which has the card inside and thought it is wise to lock the sim card so that any person who happens to find the modem will not be able to use it. I spoke to a Mike who assured me that he has locked the line. However today when I called Vodacom Customer about the same issue I was told that in fact it was never locked. I am not happy about the level of service. Judging from the information I received from Vodacom my modem was used after it had gone missing.