Yesterday (February 11), the US firm made the free iOS 6.1.1 update available to users, reports CNET.
Apple said that the update "fixes an issue that could impact cellular performance and reliability for iPhone 4S".
Last Friday, Vodafone advised its iPhone 4S users not to update to the new iteration of iOS 6, as some users were experiencing difficulty in connecting to the 3G network to make or receive calls, send texts or access the web on their handset.
In addition to the Vodafone problems, Apple also discovered some logging issues between its Mail app and Microsoft Exchange, causing some business clients with staff using the Phone 4S to block iOS 6.1.
Apple now appears to have addressed the issues, meaning users can upgrade to the latest iOS mobile software that rolled out at the end of January.
iOS 6.1 brings support for 4G LTE networks on more mobile carriers, along with the ability to purchase movie tickets using Siri.
There are also new features in Apple's Passbook app, web browser Safari, Apple Maps and music playback controls.