Question about Galaxus Mobile Basic plan

My Galaxus Mobile plan is Chf 19.00 per month but this January I’ve got Chf 23.00 but I paid it even though it’s not the same as my usual bill amount, but today I’ve received my February bill and that is Chf 59.00. Are you kidding me? They included Chf 40.00 saying I’ve send some text messages internationally but I didn’t. I don’t understand why you charge something like that without any reason?