Seller didn’t pay enough postage I had to pay additional fee

[p.boston]

Hello, I recently purchased an item the seller didn’t pay enough postage and I was fined £3.50 I am requesting the £3.50 partial refund but the seller is saying eBay will not let him do this? I am happy to keep item just want the fine payment back. Can anyone advise? Many thanks 

[jckl1957]

The seller is being untruthful as they could send you a partial refund to cover the cost of the Royal Mail 'fine'.

Unfortunately, Ebay don't get involved in disputes about postage cost and there is no way to force the seller to refund you.

[red_magpie]

I had to pay additional fee

You didn't "have to" pay the additional fee. In this situation, eBay allows buyers to refuse the delivery and use the money back guarantee to get a full refund. 

If you agree to pay the fee it's between you and the seller. eBay won't get involved.