Are replacement phones from apple unlocked?

Apple replaces your phone with the same exact model you bought.

if your model of phone was locked to a carrier, Apple replaced it with a locked phone.

Apple does not unlock phones, the carriers do.

Usually unlocking the phone is done by the provider, who informs Apple to update their data, that this certain phone can be unlocked through iTunes.

If your original phone has been unlocked by the carrier before, he has to notify Apple that your replacement should be unlocked as well.

If you contacted Apple Support to replace the phone? I had to replace mine once and got an email from Apple stating the IMEI and serial number of my old phone and the ones from the new replacement, so that I could pass this info on to my carrier, to get the new device unlocked as well.

iPhone: About unlocking

Your carrier EE is the one to talk to. Maybe try to contact an EE Senior Adviser and explain your situation.