Edit mail accounts option disabled

I've been using my hotmail account in my iPhone from like 2 years now and I want to change it but I can't access to the apropiate directory.

I know I must go to Settings > Mail, Contacts, Calendar > Add account..

But those optiones are disabled in my iPhone, I can access to "Mail, Contacts, Calendar" option but I can't press the Accounts options, they are in a more clear color than the rest. Other options like Mail, Contacts and Calendars are available.

What should I do? I've been searching this problem around the web and thru this Communities too and I haven't seen another similar problem.

¡Thanks for the support!