rude call centre agent deliberately running up charges

Rcs account payments are due on the 12th of each month. I made an eft on 12 September 2017 and was phoned at around 12:25 by a girl by the name of Phatiswa. I informed her that she needs to check her system as I am getting tired of this undue harassment. She told me that I will pay for the call which the next person will phone her with. I hung up the phone. She then immediately proceeded to make 2 more calls and this time she pretended not to hear me, thereby deliberately running up collection charges even though my account is up to date since I have already made payment on my account. It is a general culture that rcs collection staff are rude.