Failure to terminate contracts even after notice period was given

On 31 March 2025 at approximately 10H00 I contacted Vodacom to enquire about contract cancellation dates. On 09 April 2025, I emailed two cancellations for end May 2025 and got reference numbers for both emails. On 06 June 2025, I received the new invoice for June, which is due at the end of June and noticed that the two numbers I cancelled was invoiced again. I contacted Vodacom on 06 June 2025 at approximately 12H44 and spoke to a customer service agent named Zimasa, I explained the situation and she then confirmed the two numbers have indeed not been cancelled. I asked her if she needs the reference numbers and she said no. I informed her that I did my due diligence in giving Vodacom over a month notice that these two contracts were expiring end May 2025 and that I wanted to cancel them and I want a credit note for the invoices. Zimasa said she needs to log a service request, I informed her that I am not going to pay the invoice for those numbers I cancelled. On Monday 09 June 2025 at approximately 09H27 I contacted Vodacom again as I have not received the credit note. I spoke to Claudele, she then also confirmed the numbers were not cancelled and did not want to take the reference numbers for the emails I sent to cancel them. I got a bit upset that she as well failed to give me direct answers as to why Vodacom is unable to terminate contracts when they come to an end. I explained to her in a not so nice way that I am absolutely not paying the invoice for those numbers and that Vodacom has 72 hours to send me the credit note, she informed me that she has to log a service request, (Zimase who I spoke to on 06 June 2025, did NOT log a service request) and that Vodacom admin department is extremely busy and she is not sure they will be able to assist soon. I informed her that it is Vodacom's problem and that I wat the credit note for the two numbers which was billed even after the contract came to term and the cancellation request was sent in and a reference number received. It is now 4 days later and I have not received the requested credit note or any communication from Vodacom. I am absolutely not paying the invoice for that two number at the end of this month. Every time I cancel a contract that has ended I struggle one to two months post cancellation to get Vodacom to cancel the number. I also emailed customer care and received an email stating I must speak to Tobi, like wait what???? I have another two contract which ends in July and August and I am slowly losing my mind with this whole cancellation process where Vodacom does absolutely f-all.