Hi there,
I'm really sorry to hear about what happened. It sounds like your virtual machine may have been compromised and used for unauthorized activity (commonly referred to as a "zombie" or "bot"). This kind of attack can unfortunately result in unexpected high data transfer and cost.
You need to contact the Azure Support. Explain the situation, including that you were unaware of the traffic and suspect your VM was compromised. Sometimes, Microsoft can offer a billing adjustment or credit if it's a first-time incident and clearly unintentional.