My unlocked iphone 6 bought from Apple has locked to O2 when my PAYG SIM was inserted

[Anonymous]

My iphone 6 was recently damaged and I got a replacement from an Apple Store.  I have always had unlocked phones and used PAYG SIMs.  O2 is my main providor, but I have problems with the network signal at my workplace so want to be able to interchange SIMs sometimes.

Anyway, As indicated in the subject, when I tried to insert another network's SIM, I got a message on the phone saying that the phone was locked.    I contacted Apple, they said O2 had locked my phone when I inserted their SIM. This seems outrageous.  I am not tied to any contract with O2, I've always used PAYG.  I have never obtained a phone from O2. So how has the phone been locked without my say-so?  Surely I shouldn't have to pay O2 to unlock MY phone?

[MI5]

Absolutely, that is the key to answering fully.

[jonsie]

If a phone is bought outright in full from whatever source, it shouldn't be locked in the first place. I can understand to a degree if it's bought as part of a monthly contract but for CPW to use this policy for a paid in full phone is just plain wrong.