Apparently the software has problems with 3G performance which were only noticed after Apple shipped iOS 6.1 was released to the public on 28 January.
The SMS warned that people should not downloaded iOS 6.1 for the iPhone 4S until the next version. Hopefully by then Apple will have bothered to fix 3G performance problems.
Vodafone suggested that Apple's iOS 6.1.1 update has just entered developer testing earlier this week and this might fix the 3G problem. Of course Apple has not admitted that there is anything wrong with its perfect operating system.
According to its forums, Vodafone said that the update means that some customers may occasionally experience difficulty in connecting to the network to make or receive calls or texts or to connect to the internet.
"Apple is working on a solution to their software issue. These connection problems are intermittent," the forum post said
In the meantime, while Apple pulls its finger out, anyone who has not yet installed iOS 6.1 on their iPhone 4s should delay doing so until Apple has confirmed the problem has been fixed.
Curiously some Apple fanboys have posted on some sites that the whole thing was someone from Vodafone "stirring the pot" against Apple. Since such types have probably mortgaged their houses to buy the nearly identical iPhone5, it is probably best not to take their advice.