Unable to cancel account despite several attempts

I am trying to assist my mom in cancelling her account with Vodacom (I***-3). My mom lost her work and desperately needs to cut her expenses. The account is due to expire this month. I called the call center late 2019 and was told that it is too soon to cancel and my mom would be liable for over R4000.00 penalties (when the account is only R158 per month). I was told to cancel early in 2020. I called again +/- March 2020 and was again told it is too soon to cancel, and i must diarise cancellation for May and must cancel via email. I sent a cancellation notice on 12/05/2020 and have yet to receive a response. I have now sent a follow up e-mail to *** and the e-mail is returning, saying: Delivery has failed to these recipients or groups: *** The email address you entered couldn't be found. Please check the recipient's email address and try to resend the message. If the problem continues, please contact your helpdesk. We have made several attempts to cancel this account and we are still not successful. I urgently demand feedback from Vodacom else i will assist my mom in taking this matter to the CGSO. The worst of all is that this package was marketed with a WIFI ****le, which never worked. Vodacom refused to replace it and told us just to use the data in another device. Shocking! Please urgently make contact with my mom per the details you have on record. Since you record the calls, you will too be able to pick up communication between my mom and your call center pertaining to this account.