20-05-2020 12:54 - edited 20-05-2020 12:56
It won't be anyything to do with VAT unless you are on a business contract.
You must be spending on extras.
Are you sending MMS?
Have you signed up to a premium rate site.
you can check what the additional costs are for by checking your bill under Extras
on 20-05-2020 13:02
Are you on a business contract? If so the vat is exclusive of your bill, though doesn't change monthly.
If you are on a personal contract then VAT is INCLUDED in your bill.
You may want to read the other links I posted. The one about your bill will show you what you have been charged for.