Vodacom need to wake up and update their systems

I cancelled my contract and asked that my number must go on to pre paid as per 1 June 2019..the morning of the 1st June 2019 I check my balance and see that my number was not on pre paid. Luckily I was in Mosselbaai and went to a Vodacom shop, the lady who assisted me phoned cancellation department, I spoke to a gentleman and he told me I had to give a month notice and I told him I did ask the lady who I spoke to previously and did saved her call recording and she said no need to give a month notice and she asked me if I want to go on prepaid immediately and I said no only month end when my contract ends..which was NEVER processed and the gentleman who assisted me said he will do it immediately as it was a request and also going to make a note so that NO INVOICE will be generated for the new month and my last invoice was end of May which was debited on the 3rd June 2019..this morning the 9th June 2019 I received an FULL invoice even with the handset on and will be longer than 2years which was suppose should I carry on with my contract the handset must be taken off..nothing it's a full invoice generated for the new month!!I phone Vodacom immediately and the lady could not pick up anything on the system nor my Cell number or ID number and said its better I phoned cancellation department tomorrow..vodacom is quick to give a contract but it's the customer issue to get rid of.the contract and all the issues ..this is not acceptable how many times must 1 contract be cancelled and how many times must I phone to.sort out this..In went over to pre paid due to the fact I am not working and I also went to Cell C data packages because it's the best value for money for me at this stage ..hoe can Vodacom send me a FULL INVOICE and I am at Cell C from the 1 st June when they ported my number from Vodacom..is Vodacom systems not updated on cancellations or what seems to be the problem?!