Vat registry for vat exempt sole trader?

Hello, I have recently started selling on Amazon and will return a small profit and no where near the UK VAT threshold so have declared VAT excempt.

I have sent some of my product to be FBA and today have recieved an email talking about signing up for VAT

The reason they give for me needing to is due to buying my product from outside the EU and selling in the UK

I have done research and can not figure out if this is needed or not. Does anyone have any experience of this or when I could go for reliable info?

Thanks in advance for any help