iPhone 6s hotspot data usage I have unlimited data on my mobile plan which includes a 30GB allowance per month for tethering. My allowance renews on the 27th of each month, but two days after my allowance renewed I received a message from my carrier informing me that I have already nearly used all of my allowance leaving me with only 6.14 GB of hotspot data left.

The previous month I had been using my hotspot on a daily basis to watch movies via my PS4 on Netflix as well as other people using it in the house and on the 26/12 I still had 19GB left of my hotspot so I can't understand how I could then use 24.86GB of my renewed allowance in just two days. It doesn’t make sense. 

My service provider are saying that on the 27/12 I had 30GB of allowance but now I only have 6.14GB left.

How can that be?
Nobody here can answer your question, that's between you and your cellular carrier.  

Data is always reported to you on a delayed basis by your provider.  You could go over your allowance on one day but not be notified of this for several days.  

Work with your provider on how they measure hotspot data and adjust your viewing accordingly.