They made a billing mistake and after two weeks of assuring me I would be credited billed me the wrong amount anyway

Recently I was billed an installation on my Fibre line which was an incorrect amount, this needless to say made my invoice way higher than it was meant to be. After a series of upset phonecall disputes department apologized and reassured me on two occasions that I was going to be credited the incorrect amount charged and that come month end the correct amount would be debited, the credit even reflected on my app! However when the debit orders went off this month they decided to debit the full amount anyway and when I try to call customer service about it they just get frustrated and link me through to technical. The communication between departments is **** and the fact that no one can email me means I now have no paper trail of evidence to prove that I actually did not agree to the invoiced amount and was promised a credit. This is a shame because my Fibre service and Telkom Mobile service is fantastic and the extremely poor customer service and dispute handling created the worst impression. Taking money that you aren't entitled to by the contract is called *****ing Telkom and not doing what you promised is called lying! *********! Get your act together or you wont just lose the government but the rest of SA too!