When sending the item, I ALWAYS make sure that I have tracking, and that it requires a signature when received, then you have proof that they received the item, so their argument collapses. I think it's best to use paypal, as it's the safest method (when buying), though when selling it doesn't really matter what method you use. Banker's transfer is fine as you can get confirmation of payment, and evidence etc.
Hope this helps
Simon
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