The EE shops do not directly have the training nor ability to unlock phones, so the information your dad was given is correct. This can only be done officially using the website tool or by calling over the phone if this fails. They simply have different levels of system and process access, but in most cases should provide some assistance in how to go about it even if they can't directly help themselves.
Yes of course EE as an entity have to assist to unlock the device, but someone working in a store without the means to do so cannot do this.
