CANNOT BUY DATA ON WEBSITE

im trying to buy DATA for my tablet on the VODACOM website. you guys are offering 2gb for R139 and i cannot buy, not even with my card. ***, the tablet is on a 2GB MBB 24 month - TopUp. anywhere else i have to pay R149 for 1GB (WHICH IS A TOTAL ******* FOR DATA). another thing is, when i try buy DATA for my Cellphone, and i have an option to pay by card, its always saying there is an ERROR. How is a customer suppose to buy data if you guys dont get your website sorted out. i need data on my tablet, so hurry up and sort this SH#T out. WHY MUST I BATTLE WITH VODACOM ALL THE TIME. I have less **** from other networks, maybe i should go to a provider that ACTUALLY PROVIDES for the customer.