Locked to the network. They basically messed me about - not setting up DD then overcharging me and then barring my phone. I said I'd had enough of their poor service and wanted to cancel my contract. They said Id have to pay a 300 cancellation fee.
Phone companies can be so frustrating, but for the love of God, Don't sell your phone. You are liable for paying the cost of your contract in full. You need to go through the formal complaints procedure to sort this - formal complaint letter, ombudsman etc. etc.
Cancelling your DD and flogging the phone is inviting a (legal) black mark on your credit file and potentially a bailiff at your doorstep. If you keep it and go through the box ticking, you might be able to negotiate out of it with the ombudsman's help.
It's infuriating, but until you go through the formal complaints procedure, you will be in default of your credit agreement (yes phones supplied on contract are a credit agreement the same as any loan) and subject to the same penalties as not paying your credit card bill. If of course you are happy to just pay up in full and flog the phone, then go ahead, but if you have been seriously dicked around, this won't be the best way to deal with it. The ombudsman in most industries is in my experience excellent and frankly puts the wind up the supplier in most cases - generally they have to pay the ombudsman's cost for a start.
iPhones are network locked from the get go. The only way to unlock is to either go into store or fill out a form online. The process can take up to 10 days as VF will need to contact Apple directly.
But yeah as spax says, go down the official route and never cancel the DD.
A family member bought an unlocked iPhone a few years ago to use with a Vodafone SIM, but because it was a Carphone Warehouse unlocked iPhone it locks to the first SIM you put in. Vodafone didn't sell the iPhone then so they couldn't unlock it for him