data prices are not consistant

So i created an account on the Vodacom website, so i can check my balance and all of that....i see i can buy data for my devices the your website, (i have a Cellphone and a Tablet) both on different contracts with vodacom. so i decided, let me buy some data for my Tablet. i follow the steps, seeing that for my tablet 1GB of data is R79. (alarm bells start to ring) I didnt buy, <br> <br> so i selected my Cellphones number and proceeded to go to buy data for it...same as before i followed the steps. now this is the shocker, data for my cellphone is now 1GB of data is R149....<br> <br> Now i am forced to buy EXPENSIVE DATA for my phone, this is pathetic, Cellphone is on a Everyday off peak contract, and my Tablet is on a My Gb2 contract...... Why are you ripping us off like this??? So just because my cellphone is on that contract you rip me off my forcing me to buy expensive data....where i see the SAME AMOUNT OF DATA is LESS in price.. Double standards don't work here... EXTREMELY UNHAPPY CUSTOMER NOW.