Debit Horror

I hate to do this as telkom is my favorite provider and I have been very loyal to them, I upgraded my contract on the 13th April I got myself a P30 pro going for R779. I asked them what happens now they said I will pay for the 13 days on my old phone and the remaining day for the new phone and they will debit on the 30th April, I was debited R749,60 of which was not the usual amount so clearly they did their calculations. On the 31st may they debited my account for a shocking R1613,41 which is over two times my expected monthly payment. I was very confused I immediately contacted them, the call center lady said its pro-rata and I told her that was debited in April she started checking the records and could see that it doesn't make sense she said she will forward the issue and I will be contacted in 3 working days I still haven't heard anything. And today I received a new invoice stating that I will be charged R942,32 this includes insurance of which I clearly stated that I will not be taking it up and my contract clearly shows that and I went to the lengths of canceling that insurance. I don't want to experience such nonsense with telkom, I will reverse my funds and they should debit me accordingly, I upgraded my router I never had such a problem, now after upgrading my phone they do this, I am very disappointed in them.