Incorrect bill three months in a row

I did an upgrade telephonically and was promised a new contract of R576 a month and was billed R1457 a month from the telephonic phone call. I followed up three times telephonically and every time I spoke to the assistants they promised they would 'sort it out' and contact the accounts departments. Three months have passed and Vodacom is still billing me R1457 instead of the agreed upon R576. The latest operator told me it is because I activated a R1000 bundle from my side that I activated on the app which I never did, I don't even have the Vodacom app. He told me there's nothing he can do about it and I am still waiting for Vodacom to pay back the money owed to me that I DID NOT activate.