User Activity

The buyer says they have sent money to my paypal account but there is no evidence of anything. I have called paypal to see if anything was wrong but there isn't. I am now assuming that this is some kind of scam and i wish to pull out of this transact...
I have received an email from the buyer titled "You got paid for item no....". However when i log into my paypal account there are no payments awaiting to be accepted. I have updated to a premier account. All email addresses seem to be correctly spel...
Someone has bought something of me, yet they want express shipping. They haven't paid yet and are more than happy to pay for the extra shipping cost. Is there anyway i can change the amount that the item is being sold for to account for the increase ...
How do i find out they're address so i know where to post to? Do they need to confirm the payment first? Would a skateboard be a box or satchel? Apologies for how naive this may sound.