invoice

Hello,

Last week I signed a contract with O2 for the new iPhone XR. They informed me that I would pay 39.99 euros / month. When everything was done, they told me I had an extra SIM card for free and that i could use it if i wanted.

Yesterday came my bill and I was charged 81 euros for two different numbers.

The only thing that comes to my mind is that they charge me the extra SIM card so they never get informed that a fee is due.

Can anyone tell me how to cancel this other number?

Many thanks.