MTN blocked my phone

SIM Card reader 1 is not working on my Samsung. I took the phone to Samsung Repairs as it is only a few months old. Samsung told me the phone is blocked (according to: vspblackling@ vodacom.co.za). I went to the MTN Sandton store a few weeks ago and they told me that my phone is not blocked. I called MTN again today and they now say the phone was blocked but they do not know why they blocked it. This has been ongoing for almost a month and I have been an MTN subscriber for many years - never have I had this issue before I need to know the following: 1) Why was my phone blocked 2) What is the process to unblock it