If the seller is asking for a different shipping charge, ask them why. Possibly you selected an incorrect shipping option, or you are rural but paid urban, or the seller is pulling a fast one. Many options and you need to find the facts of the issue before you can assess it

Callum, yes I have lots of question marks about this buyers statement, was just throwing it out there to see if its possibly a thing. But as I say I seriously question  the authenticity of the buyers statement

Guess its a pretty good way for a company to minimize compaints againt it, very disingenuis 

I suspect TM is bound by TM natural justice. So Both buyer and seller are bound by a "reasonable" time to reply which extends the process . Its reasonable to expect that a trader maynot be on email often to need to allow extended periods to complete claims. Yes, its a pain but in the big picture resonable. But certainly not helped by TMs lack or humans to expedite queries once replies come back to TM. But that is normal , as companies become larger, their customer service gets crappier and crappier

I belive if no charger was pictureed or mentioned, then they only get what is advertised, they are effectively asking for an item you are not selling, or looked at in another way , asking for an effective huge discount for you to supply charger. This is the buyers issue, not the sellers, although as Callum suggested, would have been a good idea to mention it was not included.  I would tell them that if they dont want to go ahead with the trade, they can return to you at their cost, and you will refund the "purchse price", but not outward shipping. I think Callums suggestion of refunding shi...

Im guessing the parcel was quite large volumetrically and in these cases, even though the weight is low, they calculate a volumetric weight whch is im guessing the 11kg you have printed on the ticket. However that pricing should have come out on your original calculation, Is it possible that the original shipping price was based on urban delivery and you are sending to rural so has extra charge. Or possibly on either your original calculation, or final calculation for shipping costs, did you input an incorrect figure leasing to the variation between costs?

It is clearly feedback black mail, which TM look at in a poor light. From the TM feedback policy "As outlined in our code of conduct, members should not replace retaliatory feedback. " It maybe best not to mention this to them as otherwise they may manuipulate the wording of the negative to make it look as though its not retaliatory. But if they go ahread with it, you can do a feedback dispute with TM and you have the email to show TM that it is retalatory.

Im on standard as Callum, no VPN, but have ad blockers

I also have exactly the same issue as alan with firefox . I also find I cannot contact TM on firfox through the chat bubble, so go over to chrome for these activities. If I was soly on fire fox there would be no possible way to contact TM, as it both blocks chat bubble and all the other messaging to TM

Absolutley, as L says. However reporting them to TM maybe a waste of time as if it was a genuine mistake, by not completing trade at the original price, they are following the law of the contractual mistakes act, and TM authority is not above the law. But it maybe good for TM records if this was an on going recurring situation