Vodacoms bad practices

I phoned Vodacom in December 2018 to cancel my contract, they offered me a package that included 5gb of data and an airtime value. Unknown to me for 7 months I did not receive the 5gb of data as promised but paid the same monthly fee. I am very disappointed that the only assistance vodacom was willing to give is to restart my contract as of the August 2019. I feel i should be compensated for the past 7 months, they offered to give me an extra 5gb once off which does not equate to what I paid for. This is disgusting service!