MTN - Bad service all around

I am truly appalled at the pathetic service I am getting from MTN since the day I took out my contract. First and foremost I was never told that the phone they are giving me only comes with 1 sim card slot. 2ndly your call centre agents are rude and don’t know what they are doing. You call 3 different call centre agents and you get 3 different stories. No one takes responsibility for my query. I am trying to change my contract number because I can’t use the benefits of my contract on the number they provided me with, because my main number is the prepaid number. I have a prepaid sim card and want to use that number as my contract number. 1 person says to speak to the customer service department. Another says to speak to the department where you have opened the contract – the lady said hold-on and dropped the call. Called back and another says go to the store. I went to the store only to be told it can't be done. Who should one listen to - I am confused?