Hey @Rebeca_28357 I can understand your concern and while I can't discuss specifics publicly I would be happy to help advise you. First thing I'd recommend is checking the bill to see what the additional charges are for.
While the plan is €40, if you are using the phone outside the EU without allowances or contacting premium numbers not included in your plan these would incur an additional charge and you would be able to view the full breakdown by going to My3 and then in the Amount Due tile you can also see the View Bill option.
