I called to cancel in November of '16 (card was up for renewal that month). They offered miles (which I passed on due to a large balance that I can't find award seats to use - but that's another subject...).

They then offered a cash credit of $250 if I hit a spend target of $3K per month for 3 months. I had the girl repeat the offer back and she changed the details each time she repeated it, first the target was $3K total over 3 months, then $3K PER month.

Fortunately after going around in circles a few times, I asked that she email and snail mail me the details in writing (smart move!). The final version of the offer was $3K spend target for 3 months and a $250 credit PER month for the first 3 months. Keep in mind that the annual fee is $450 - so I agreed and hit the targets. It took a couple of phone calls and escalation to a supervisor, but the full $750 credit posted. In effect Citi paid ME $300 to use the card for a year!

Good luck - but if you accept a retention bonus, be sure you get whatever is offered in writing.