This was exactly my problem, any time I tried to disconnect my Twitter account from Ask.fm there wasn't an option to remove it. I tried everything and nothing worked, but today I found out how to do it.
Many people have their brand new iDevices, and now with the release of the iPhone 5 the question will resound even more: how to create an iTunes account without a credit card?
Well, it's exactly the same way as creating an account with a credit card, only with a slight difference.
So, on my Twitter account sometimes it useful for me to upload two photos in one single tweet so people understand what I'm talking about, the thing is, I couldn't find out how to do it!
I use Tweetbot on my iPhone, once is the best Twitter client I've ever came across, it's definitely worth its price, so check it out on the AppStore and buy it!