We had signed up for Citibank's AT&T Universal Rewards Card to avail a $100 sign-up bonus. Once the card arrived, we activated and made a purchase with it. When the first statement arrived instead of getting 10000 Thank You Points we were given 6000 points. We were really surprised at this change. We called Citibank's customer service. They informed us that the current offer on the AT&T Universal Rewards card was awarding only 6000 points instead of 10000 points! The 6000 points were worth $50.
Being disappointed at this surprising change we challenged the customer service representative. We averred that we had signed up for the offer online and the deal was for 10000 points. The representative listened patiently and told us to send them a copy of the offer. We went online and searched for the offer we had used, but alas it was available nowhere. Since we had not saved the offer as a pdf file or as a paper printout we could not send them the offer. Consequently we had to settle in for 6000 points instead of 10000 points.
From this experience we have learnt to keep a copy of all the offers that we use for sign-up bonuses. Also, note that the credit-card companies can change any offer at any time without notifying the customers. So until we get the money in hand we have to keep our fingers crossed and hope that it comes through!