User Activity

buyer never picked up items. I'm worried about the actions i have been advised to take. I don't want to upset someone i don't know when they also have my address.
Buyer hasn't showed up and won't reply to my messages . The auction ended 24 days ago. What do i do now?
I tried selecting contact buyer and all that comes up is a space for me to message them. Nothing comes up reguarding invoicing. I sent buyer invoice with too little postage charges.
Made an error on invoice. Need to add more postage , can i send another invoice? If so how would i do this?
Sent an invoice with incorrect postage. can i send another invoice as i need to add more postage charges?