iPhone 4S customers have reported issues accessing 3G.
Vodafone reported a BlackBerry service outage across EMEA last month, which left users angered without access to BBM, Twitter, and emails.
Now, the operator warns iPhone 4S users to avoid upgrading to iOS 6.1, as owners are experiencing patchy 3G performance. The signal glitch is preventing customers from connecting to the network properly, which is causing issues making/receiving calls, texting, and connecting to the internet.
Phil, part of Vodafone's tech team, said: "Apple is working on a solution to their software issue. These connection problems are intermittent.
"We would recommend that anyone who has not yet installed iOS 6.1 on their iPhone 4S should delay doing so until Apple has confirmed that their problem has been fixed. They haven't provided us with any timescale on resolution at this stage."