Refusal to redeem picnic voucher

Groupon offered a picnic voucher at the wine estate with a expiry date of 17 December 2014. Prior to that date we phoned to make a booking but was informed that they could not accommodate us due to the high demand but that the validity period of the voucher would be extended to end February 2015. We phoned on a number of occasions towards the end February to make a booking but the phones were not answered. It appears that the lines were down because of cable theft! When we finally made contact we were informed that the voucher has expired and we can no longer make use of it. At no time was there an offer of a discount on a full picnic price or any product or any alternative.<br> Two days later Groupon are offering a voucher for the same picnic at the same price at Mooiplaas. Perhaps someone at the estate can explain the rationale behind this strange brand of customer service.