O2 customer support are sure to have had an ear-full after signal problems lasted over 15 hours.
Issues were reported across the country, and were not location specific but seemingly random.
When probed for a response O2 helpfully said that a problem occurred 'somewhere' and engineers were working to fix it, no time-scale was given.
2G was restored at around 10am Thursday, with 3G still experiencing problems.
Many vented their frustration on Twitter: