Mtn is robbing me.

My name I lisdia Mrubata living I Cape Town, I have a contract with mtn for a phone which I am currently paying and sometime last month at about the 20th I received a call from a person claiming to be working at mtn and he ask me to give a OTP number on my messages and claiming to sort out what so call a problem with my contract so I ask him that why he doesn't refer me to mtn so I can ask questions two, I then gave 3 of the 6 numbers and I stopped and I told him I go my self at the store which I did and ask about the call and they said it was a **** and the guy who help says that he will stop it, then my son called the head office and explained the Metter and they said it was a **** and they stole from my contract account R1800 which I now have to pay. What make sad is the fact that they don't want investigate this metter I must just pay back the money including my installment for every month's and I payed them R2000 so I don't get hole seccuation I feel like MTN Is robbing me first of all how did this person get my information I mean the is a poppi act is our information safe with them.