Frustrated

I recently changed jobs and do not receive my salary on the same date as previously I therefor changed my debit order date to the 7th of each month. I did this via Vodacom chat on the 8th of July, my debit order for end of June did not go off from my bank account for this exact reason, I went to Vodacom in Clearwater mall and paid that outstanding debit order via eft, now all my lines are blocked, I went to Vodacom and they told me my account is in arrears and the payment I made does not reflect on my account, I had to drive all the way back to Clearwater for proof of payment, I get there they are telling me my account is in arrears how is this even possible if every single debit order went off from my account except the end of June one where I went to go pay for it inside the shop? This is just something that boggles my mind I can not be in arrears with my account I never missed a single payment now they want to deduct a double payment from my account for what reason? Everybody is just saying we will log a complaint and look into this matter, that is all answer I am getting are they trying to rob me of extra money that I can't afford, I have been a loyal customer for many years