I can't find the recent blog post about Citibank converting cards to no pre-set limit World Mastercards, so I post my experience here (maybe you can move it to where it belongs? ;-)
Ever since that blog I was on the look out for any mailings from them. The first was from AT&T Universal Card (which is run by Citi). In their announcement letter they actually offered an opt-out option, so I called that phone no. and it was an automated process. Thus, it seems I'm fine with AT&T and they won't convert.
Today I got a similar letter for my Citi Dividend Platinum Card. That one announced first that the 2% cashback earnings for special categories such as groceries, gas, etc., will phase out starting in July and everything will be 1% cashback. The 2% will be replaced by quarterly special categories that earn 5% (similar to Discover). The second part of the letter then contained the bomb shell: my card will become a Citi Dividend World Mastercard with no pre-set limit. I immediately called them and ended up in India with a crappy phone connection:-( That CSR couldn't help me, even after supposedly checking out all the options and talking to some supervisor. I was less than happy.
So, after half an hour I called again and landed who knows where in the world (but better phone connection and much less of an accent;-)
In the meantime I had looked at other Citi cards to figure out to which type I'd like to convert my Dividend card (in the small print at the bottom of the letter it said: To receive the replacement card, your card acccount must be open and not default under any Card Agreement you have with us at all times. if your card account is closed for any reason, including if you convert to another card product, you may no longer be eligible to receive the replacement card.) - hence, I figured I could convert my card. Alas, the CSR told me right away that they don't do conversion anymore(!) - hm:-( However, he was very helpful and said he'd look at my options since I've been managing this account for almost a decade now in an excellent manner. He would talk to his manager to see whether I could opt out of the conversion. After a rather long musical interlude of a quite dubious quality the CSR offered me the excellent news that I've been opted out of the World Master Card and won't get converted.
I asked whether I'll get something in writing that would confirm my choice to which he replied that unfortunately not. However, he gave me his name and batch ID number. All in all, the second call was a positive experience for me, especially after the first call after which it seemed there was no flexibility on their side. I'll find out in a month or so I guess whether my intervention was actually effective...
Lesson learned: perseverance might get you what you want:-D