Data On the Go 10GB SIM-only plan but receiving 500 MB

Data On the Go 10GB SIM-only plan. I logged a complain on Facebook from March complaining that my data is depleted within 5 day . On my device I have Facebook , snap chat and IMO. I don't have any other social network. I use my router during the day and at home I am connected to another WIFI. I called in around March to complain and the consultant confirmed to me that I receive 500 MB. I top up with 2GB and its last me entire month. I have signed up for 10 GB , 5 GB during the day and 5 GB at night of which I am not receiving. Please advise on the cancellation process as the service I am receiving is not what I signed for .