Vodacom bad service

I have a data account with vodacom I lost my job February I struggled to paid called several times explained that they must atleast reduce my installment they refused, then may I got another job called and told them to deduct they did not deduct on the aggred date I ended up in arreas had to pay a lot of money, now I called on the 23 of July to ask for account number to make an online payment they person told me they are going to deduct on the 28 I told him I don't trust vodacom because they don't normally deduct on the aggred date then he said but you are not in arreas I said is OK I don't want to be in arreas I made a payment same day on the 23rd, I was supprised to see on my statement that vodacom tried to deduct wherelse I made a payment before, when I call I get a different story that on the 23rd I was paying for June and what supprised me is that I made a double payment can't they break it into June and July hence they say I was paying for June and now I'm told they will charge me extra 100 because the debit bounced back