Want to cancel a sale. The buyer has not paid in after more than a week, and keeps aski...

Want to cancel a sale. The buyer has not paid in after more than a week, and keeps asking for invoice that I have sent three times. *The buyer also refuses to confirm receiving the invoice and claims payment has not been made due to me not combining the shipping fees, which I have as reflected on the invoice that I cannot confirm the buyer has reviewed.*The buyer could also calculate the combined fees themselves if they were in fact motivated to complete the transaction. *At this point I do not feel comfortable doing business with this individual and am leery of shipping any merchandise to someone who I don't feel that I can't trust.