Dont keep promises on promotions

When renewing my contract with Vodacom there was a "Made for summer" promotion running, whereby you got a Flight Centre travel voucher to use as part of the package and promotion at Vodacom. It was a process just to get the voucher by sending sms's etc. Futhermore we were advised that we must make a booking 4 weeks prior to our travel date, thus you had to plan ahead. Now, when attempting to use the voucher, we were informed by Flight centre that the voucher had expired. My wife spoke to the people at flight centre, stating that we were NEVER informed of an expiry date. The manger phoned and said that we had signed a T&C's where the expiry date was mentioned. We explained to her that no where was there an indication of an expiry date, not even on the T&C's she continued to argue that it was there. My wife then requested her to send us a copy, whereby she said that she can no longer provide it to us, since the promotion is over. This is unacceptable, if we were informed of the expiry date then we would have made other plans, now our holiday is booked, and we cannot fly there because of this! How can you promote something and then not deliver on your promises? I then had a look at the paper I had to sign in order to get my voucher code, and nowhere is there any indication on the T&C's of an expiry date. Thus you must meet your promises and allow us to use the voucher, otherwise it is false promises and advertising by Vodacom, Samsung and Flight Centre, especially if you cannot proof to me on the T&C's of an expiry date!