UK mobile operator O2 has promised to do everything it can to make it up to its customers following the network outage.

Full service resumed on Thursday afternoon and the company tweeted: “We want to restore confidence and trust.

“We will be doing everything we can to make it up to them in an O2 way.”

Customers started to suffer problems on Wednesday lunchtime after a fault with one of the operator’s network systems meant that some mobile phone numbers were unable to register correctly on the network.

However, on Friday the company said it had still not identified the root cause.

Informa analyst Francesco Radicati said O2 has dealt better with this problem than other operators have done in the past.

However, he criticised the company for not being proactive enough “to avoid giving customers a poor perception of its service”.

There are further concerns about how the UK’s mobile infrastructure will cope with the influx of visitors for the Olympics, which start at the end of this month.

Ovum’s Steven Hartley said the country’s mobile networks already have a poor reputation compared to others in Western Europe.

“The UK as a whole must rely on previous investments to carry it through – and these have been less than optimal in the mobile space,” he said.