MTN giving me problems

<p>i terminated my contract with mtn in 2015,last year i found out there was an outstanding amount of R381 which my sister paid into their Absa account,now im being harassed by SAYA recoveries telling that i still owe MTN an amount of R681.36,when i asked where all this came from they dont know,the whole of last i tried to sort the problem but whenever i called MTN no one was willing to help,i even tried MTNSA which i never got through,now they tell me that if i do not pay they will to blacklist my name,my issue with them is what guarantee do i have that they will not ask for more money after i paid and also why am i still paying after the contract was supposed to have been ended in 2015</p>