I've been with o2 since I was a child, I'm now 25. I had never had any problems with o2 until I recently tried to upgrade my phone.
Without going into too much detail, they basically fudged up the upgrade and made me return the handset and said I had to go through the whole upgrade process again. All because of their own misleading sales team.
I was left without a phone for almost 2 weeks as things were delayed etc. Made a complaint and they did actually resolve it well and to my satisfaction.
Will continue to use o2... for now anyway...! :)
To reply as a company, please log in to your business account.