Migrated to a higher option without consent.

Vodacom doesn't even deserve a star. On the 30th on November I received an email about migration quotation, which I ignored because I know I never spoke to anyone about migration. Today I received the invoice and a statement that shows that the line has been migration to a higher option. I have never gave a consent to anyone to migrate the option I was using. I cannot even afford to pay the option they migrated to. I need it to be downgraded ASAP.