query with tesco online shopping..?

[looobylooo]

hi all,
can anyone give me help please with regards to online grocery shopping at tescos..?
i registered tonight on their site and shopped for the first time online.
some of the items are on offer - ie 2 for 1 etc
but my final bill at the checkout is the full price with out the offers deducted..
it says do not worry because the driver will deduct the offer price when my items are delivered.
so, how does this work please? - is the full amount taken from my debit card and the driver then gives me change at the door...?? is this right??

im sitting here not finalizing my transaction until i know for definate how it all works, so im hoping someone kind soul will offer me some help asap! lol
thanks