Messed up Telkom billing services account escalation with wrong payment history

I have an account with Telkom for years but recently, the invoicing is not making sense. The mistake I committed was to change banking details. we were debited twice for one month opened a case with no feedback then we got calls that we are going to be blacklisted from NuDebt management, when I sent them out payment history they responded and said they cancelled the account we must contact Telkom which is extremely hard to reach