promised 4gb only receiving 2gb (Vodacom refuse to listen to sales recording)

I have tried to sort out this problem with Vodacom since 10Sept and still not one person at Vodacom could rectify my problem .The call centre is useless transferring you from the one department to the next .

I wanted to cancel my contract with Vodacom (after the 24 month period) But they persuaded me to take a special offer .The 2gb package but you receive 4gb anytime data for 24 months .So I gave in to the special and told them send me my Wi-Fi router :-) .

I use this Wi-Fi router for studies at Unisa to submit tasks etc. but half of each month I see that the 4gb is gone already only to find out they only giving me 2gb of data :-( ...

I asked Vodacom to please add the extra 2gb of data (AS PROMISED) or cancel the contract that they broke with me .

Also Vodacom refuses to listen to the sales recording ( I have my own copy of the recording)

So once again Vodacom PLEASE ASSISTS (If I have to buy an extra 2gb each month it will cost me R6000 over the 24 months )