fail to disclose information to a loyal customer

on the 7Th May 2015 I was due for an upgrade , I went from a voice contract to a tab 4 ( data option ), the reason for my upgrade was for a gift to my spouse for mother's day , I never used my voice sim card ever sins I'm with Vodacom , when I upgraded I made a Sim swap to a sd card and was told to put in so it can activate in 24 hours , I was told that my data will start 1 June 2015 but was not told not to start using the card to browse and must only use it 1st June , was also not disclose to me that if you use it now it will be on airtime and not on bundles and it will be expensive , if that was explain , I would of just leave the sim card like always and waited till 1st June. now that's not all , having the TAB now for 10 days I receive an sms stating my bill is due R4800 for the month of June ( usage was 2GB ) , you cannot just expect your client to know how all options work , which was assumed to me when I went back into store to query. imagine I was on voice contract black berry for years , first time going to bundles how can I now that and imagine paying R4800 for 2GB only and still need run the contract for 24 months paying R269 , in total R11256 for Samsung galaxy Tab.