Unfair charge

I pay Telkom using eft every month on the 1st and dont use debit order facility. They confirmed all my payments are received but now they want to charge me a penalty fee of 407 mainly because the payment reflected on the second. I asked Bianca from the call centre to assist and she just didnt want to see reason. I told her that i wanted to upgrade to a new phone and this issue is stopping me from upgrading with them she basically didn't not care about retaining the client. They have the worst service i have ever experienced in life. I am very angry with how my issue was handled. She doesn't care and more Bianca is a senior at Telkom.