Why do i have a high bill?

TRYING TO CHARGE ME 380€ for 1 MINUTE!!!
I had simyo in another country and it was amazing so that’s why I chose it over others in the Netherlands. 
I’ve already been charged before with extra money because of my internet consumption and I was aware that this could happen so I took all the advices they gave me to prevent it(no updates without WiFi, no apps open that I’m not using, no downloads without permission first..) and it haven’t happened anymore in over 10 months. 
They upgraded to 40gb which of course I never fully used and suddenly in one morning while I was not using my phone they are telling me I consumed 20gb. 
I first received a text saying I used already 80% of my internet, was really surprised about it and proceeded to check how much I had left for the rest of the month which was 6 gb for 3 days so I was thinking I was safe of course. 
Exactly 32 minutes later I get another text saying I already used the total amount of data so I proceed to put my phone in airplane mode to avoid any extra cost, and didn’t use the phone anymore until I got a WiFi connection. 
I was really confused, and checked mi app again which said I still had those 6gb left, at this point I was scared but I was thinking this might be a mistake. How is this possible? Took all the screenshots to prove what my app was saying. I DIDNT USED THE PHONE AT ALL, HOW CAN THIS HAPPEN? 
One hour later I get a text saying my sim card is blocked because of my consumption. 380€ IN ONE MINUTE !!!!!!! HOW IS THIS EVEN LEGAL ? 
They sent me the text at 10:39 which i have prove in my phone and they charged me this INSANE AMOUNT from 10:38 to 10:39. Excuse me ??? They even started charging me before sending me the text. How ?
I made contact with them and after trying to explain the situation which they didn’t care about, they said the only solution is to split the bill. I was not happy with this and I ask if there’s any office to discuss this in person and show the prove in my phone. They sent me to a location and when I went there nobody could help me because I should make an appointment first, but this was not even mentioned. I contacted them by phone again and asked if he was in the office to talk in person but he refused to help me, he said he would just do it by phone. Tried to get an explanation about how this is possible to happen and what was the internet used for, they say they cannot give information because of privacy matters. I again ask for help about this matter and they say they won’t help me because they did it previously (2 years ago) and the financial department don’t want to approve it. I ask the guy of customer service to provide me with his name and surname and he says he is not going to do that, only name is enough. In which company is this normal ?
How is it even possible that you won’t give any help to a charge of 400€? How is this normal when I have to be working a full week to get that money ? How is everything in world like groceries, electricity and water supply getting more and more expensive and a company thinks is moral and right to charge this for a 1 minute consumption? 
Made some research and talked with people I know and there’s many more with the same problem. 
I will continue fighting about this situation and will ensure everybody I know gets to know about this, but i do not trust this company anymore and I refuse to stay with my arms crossed while they are trying to take this insane amount of money from me and I can prove everything in my phone, app and website.