You might speak with advanced Apple Support on this issue to see if assistance can be provided in resolving the matter.
In principle replacement devices should carry the same activation policy as the original device.
There may be a deficiency in the database maintained by EE and you could instead escalate the matter to a higher level with the carrier.
Alternatively, you could review the terms of your contract with EE and file a dispute if indeed an unlock is warranted under the policy intent.