Mtn I have never received any new phone

I have few contracts with mtn and they were running smoothly until earlier this month. In around the 9th of this month (February) I received a call from mtn lady notifying me that my other no which start with 082 due for renewal. I told the lady not to bother because I don't do upgrades on the phone I will visit mtn store. There after my phone stop ringing no more calls coming in. I called mtn 135 is blocked have to use another phone to get through. The champion advice said she is seeing no fault , in my account she refreshed the SIM card , and my problem persist. On the 20th of this month I went to Bloemfontein Mtn and there they couldn't see anything wrong....and they did sim swap and the problem was solved I could receive calls. The following day I realized that my data is depleted,I called immediately. Was informed that on the 10 February I have done upgrades on my account and have also received sumsan a65 cell phone. I have never received any cell phone or done any transactions over the phone. I would like to know who used my particulars. Why it took so long to realized that ***** has happened. What would it take to get back to my old account.