Not Providing what was Agreed

I upgraded my contract in Dec 2017 and was promised that I would receive 10Gb of data every month. Come 01 Jan 2018 when my new package comes into effect i am told that this data was a once of promotion. I cannot accfept this as i queried this distinctly with the consultant when taking out the upgrade. Did a follow up on the 3 Jan 2018 with them and i still have not had any feedback, vodacom are unable to communicate internally with their different departments so what are the chances of consumers being able to. Not letting this go! Disappointed again in Vodacom!