Beste antwoord door Dolphin
Welcome to the forum.
It's not wise to post your telephone number here. A mod will probably remove it for you.
For your question.
Go too www.t-mobile.nl and login to My T-Mobile on the right hand side.
After login, on the top under 'facturen' you will find you're invoices. There you can see why you paid 28 euro's and, if necessary, you can also see if your contract is still valid and what discounts you receive.