hallo 
i have purchased a prepaid sim card from O2 store which have 6 GB on its cover with 19.99 Euro for 4 weeks.
then i have discovered that, the real price of the sim card is 9.99 Euro including the 6GB data. And he charged me with 10 Euro for service fee !!! 
He explained it to me as the following; 9.99 Euro for the sim card and 10 Euro for the 6 GB.
and give me 2 receipts with one with 9.99 and the other one for service 10 Euro.
after i went to another shop i have discovered that the price of the sim card including 6 GB is 9.99 Euro.

so is their any service fee should be paid upon purchasing the card or activation fee ?