What network is it locked to and how did you come to own the phone? Was it on a contract that has now ended? Bought payg and you wish to change provider? Or bought second hand?
By law they have to unlock them for free when a contract ends if you request it but if not EE do it for £8.99 anyway. Try here https://myaccount.ee.co.uk/device-unlock/
Not really, they will charge a tenner minimum and if you're willing to pay that then for £9 EE do it via a phone call without having to leave the house. 0800 956 6000 option 2 then option 4
Good advice there SuperTyke. Should always look at existing provider to unlock first. Can even be free, depending on your contract terms.