SIM ACTIVATION HORROR

I received my tablet package on Friday and I called the call centre for sim activation-I was then advised the sim card will be active in 24hrs which means on Saturday-Saturday afternoon I then tried my new gadget received my new number and then 5 mins later the sim give an error of sim not registered on the network,called the call center and did not get any assistance then gave then until today were I called and still my sim only reads the network for 2 mins then it would say not registered on the network, no service or emergency calls only...I am very frustrated coz now I am being told I should go to cell for them to check if the fault is with the tablet of the sim card...I ask when coz I get home at 7pm and I am running out of the OBF window period the next thing u know is if the fault is with the handset and the OBF period has expired my \NEW"tablet will be taken in for repairs...not a happy customer at all :("""