O2 customers who buy either an iPhone 5S or 5C won't be able to connect to the operator's 4G LTE network right away.
That's because of a technical issue that will require the input of Apple to resolve. And that's not expected to happen straight away.
"The iPhone 5C and 5S will ultimately work on O2's 4G network, but we are currently waiting for Apple to enable the carrier bundle for our network,” a company spokesperson told TechRadar.
"We've been advised this will be in the coming weeks. We want to be transparent about this with customers, so we are giving 5 off, and clearly they'll still have 3G connectivity until the carrier bundle is enabled to allow 4G [for the new iPhones] on our network."
In better news for the telco, O2 has revealed that both handsets will be available on its Refresh package that allows users to upgrade their handset mid-contract – useful for those looking to get a cheaper 24 month tariff but who are likely to want to upgrade again come the rollout of iPhone 6.