Incorrect billing

Around December 2016 I went to PMB MTN to request a settlement amount for my contract which I had with them. I was told to call to get the amount. I went home called, the reference of the call is *** and I was told I have to pay R1941.86 for my account to be closed. On the 25th of January 2017 I went back to the MTN branch to pay the amount I did and I have proof. Now I am getting emails that I owe MTN R2047.89. What am I owing because according to my knowledge the account was closed January 2017. Kindly assist.