Thank you for your question, my name is ***** ***** I am a fully qualified vehicle technician with over thirty years in the trade, I will try and help you.
It would appear that the DVLA have got the details of your vehicle wrong, the supplement to the tax is due on vehicles costing over £40,000 and as the list price of you Kia is around £10,000 the details at the DVLA will need to be changed and to do this you will need to contact them via the website, at the moment due to the Corona virus no other communication is being accepted.
To contact them click here
Click the top box on the form that will appear and then continue at the bottom of the page, then click vehicle tax on the next page and continue at the bottom, then click any other tax enquiry and again continue at the bottom, next click the cost of vehicle tax and again continue, this will finally take you to a page that will take your details.
Once the DVLA have your details they should contact you with regard to changing the tax rate and correcly listing the purchase price.
Unfortunately the service is slow due to the Corona virus situation but they will eventually sort the problem out for you.
I hope this answers your question but do please ask any further details by replying to this thread.