[mcpvperz]

contacted them via live chat and got told this

At first, they didn't want to escalate and just told me that they confirmed the delivery so I applied pressure and got told this

"I will escalate the case to another department for further investigation. We will get back to you via email"

Good work with applying pressure.

It clearly demonstrates that It can be escalated If you're prepared to persevere and not take "no" for an answer.

I received this through email

We want to inform you that Instabox has told you that your order XY  was delivered in person without your permission to leave the package outside the door. You have also given instructions to the driver that the name of your door is XY.

We will therefore not be able to assist further.

I mean I didn't give any instructions?  it just asked for my name on the door when entering my address information. Also, they completely ignored my request to provide proof of signature

I'd chat with them back and tell them exactly what you just said. You never gave instruction and that they completely disregarded your signature.