Which of the following is considered NOT acceptable as a payment method?

Unsigned credit cards are not considered an acceptable payment method because they lack the signature verification that is required for authorization. A signed credit card provides assurance that the cardholder has authorized the transaction, thus protecting both the merchant and the cardholder from fraud. Without a signature, it cannot be confirmed that the person presenting the card is the legitimate cardholder, which presents a risk for both parties involved in the transaction.

Money orders, Sure Money wire transfers, and pre-canceled stamps, on the other hand, are all valid forms of payment as they provide a reliable means of transaction that can be verified and processed according to established protocols. Money orders are prepaid and can be easily traced, while wire transfers are a secure way to send funds electronically. Pre-canceled stamps can also be used as a legitimate method of pre-paying postage, making them acceptable in postal transactions.