How to get rid of VAT

It's probably the namekey that you configured for your tax rate.
Go in the System>Taxes menu. There, click on the "manage rates" button.
There, create a new tax rate and enter the text you want instead of "VAT" in the namekey and the percentage of the tax rate.
Then, go back to the main System>Taxes menu, and edit your tax rule. In its "tax rate" setting, select that new tax rate you just created instead of the old "VAT" tax rate and save.

Also, it could come from some translation texts. So you can go to the HikaShop configuration page, under the Languages tab, edit your language file, and there you can search for the "VAT" text and replace it in translations.