I know an older couple that recently signed a contract for a specified number of points for a specified dollar amount. The contract allows them to cancel within 6 days via certified mail. However, they sent the cancellation via registered mail, return receipt requested (which takes longer to arrive). It's now a week beyond their 6 day cancellation period and the USPS still has not delivered the letter. Once it finally arrives, can the company refuse to accept the cancellation on a technicality since the letter was sent via registered rather than certified mail as specified on the contract?