Samsung buy and get voucher query

We purchased a fridge and received the Samsung buy and get voucher. According to the information received, all bookings must be made within one year of receiving reward registration PIN code. Actual travel must take place no later than 31 July 2019.

Our pin was received on the 13th February 2018 and we are now attempting to make a booking only to be told that the voucher has expired.

We have called the customer service team on 18/01/2019 a few times and we received different information as well as having the phone put down while we were holding on. We requested for the matter to be escalated and we were told we should receive a response by the end of the day. We have still not received feedback.

We need to book 4 weeks in advance and due to lack of feedback and assistance we are unable to book at this point.

Can I please receive urgent response as to why the voucher has expired.