Apple has released iOS 6.1.1 for iPhone 4S devices to fix 3G issues that carriers warned their customers about with the iOS 6.1 update



From MacRumors:

A beta of iOS 6.1.1 was released in the middle of last week carrying a build number of 10B311 -- it's likely the upgrade released today was a urgent bug fix and the prior 6.1.1 beta sent to developers will become 6.1.2.

  iOS 6.1.1 released