A lot depends if this a PAYG or pay monthly SIM @Moiko , if you were able to mention the service you are using, the thread can be moved to the correct board.
Follow this link from help and Information How do I activate and set up my new SIM?
If this a PAYG SIM, Vodafone will automatically convert your top up into a Big Value Bundle, if you don't want a Big Value, the trick is to op out before topping up here : Remove Big Value Bundle Further information here: PAYG
Additional help and information here Getting Started
