My shipping cost disappeared !!

[r.soles_sneakers]

Hi

I had a listing for some jeans for £110 with £4.20 shipping ( 114.20 total) 

when you have watchers you get the option to send an offer which I did for £80. 
a buyer countered it with £70 which I accepted and now in the sold section it shows £70 and shipping is free and I have to pay for it ! 

how comes the shipping price in set at £4.20 has disappeared ? Iv made many counters and sales like this before but on this particular item all of a sudden it's become free shipping .!?

 Anyone else has this problem because eBay has said I'm the only one. 

if you click on the sold items it shows the jeans sold for £70 free shipping

 but if you continue clicking to go back to the original listing prior to the sale I clearly have the shipping price of £4.20 displayed !

 Is there now an option where the buyer can counter a price and select the shipping for free ? If so it doesn't show me 

any help as eBay haven't the foggiest and they said I put free shipping even though on the original listing it clearly says £4.20 shipping

 hope that makes sense