Activation and porting *** on the wrong date and billing me ***

I am planning to move and I have cancelled my Fibre account alongside with VOIP end of May 2021. I have then decided to port number *** to Vox Telecom at end of May 2021. However Vox telecom has billed me from the date I submitted my FICA document and they have started billing me even though my instruction said it was end of May 2021. VOX kept on spamming me with sms and emails but ignored my e-mail and instruction to cancel. They either do not answer their phone or they do not reply emails but now they have told me that my account is in Cash payment. I am thinking about cancelling my request completely seeing there is simply no customer service so why would I even bother to use their service.