O2 has revealed that its IT systems are back to normal, after demand for the 3G iPhone caused its web site to crash and store systems to slow last week.

An O2 spokesman told Retail Week: “The average time for selling a contract in-store is 20 minutes. While initially on Friday our systems slowed and the process took longer, we were quickly back to selling iPhone 3Gs within the business-as-usual 20-minute time frame. All our retail systems are now working on a business-as-usual basis.”

However, he added that O2 will not sell further stocks of iPhones through its online store, until “we are sure it offers the best possible customer experience”.

Some customers who snapped up devices from one of the first batches released also found that they could not use them straightaway. On its site, O2 warned customers who were new to the mobile operator that they must have their phone activated by O2 and synchronised with Apple’s iTunes software before it will work. O2 admitted that the activation of the mobile service for new customers could take two to three days, given the volume of sales.

The spokesman explained: “The vast majority of people who purchased iPhone 3Gs on Friday had their accounts activated fully by Saturday. There are customers for whom it is taking slightly longer and we are working to activate their accounts as quickly as possible.”

In addition, it has been reported that customers also had difficulty accessing the Apple web site to download the latest version of iTunes.

O2 says that details of further availability will be published on its web site, with individual stores using window signage to show whether they have the product in stock.