Not receiving texts from users on iD after porting to EE(Lyca)

Since porting my number from iD to EE(Lyca) I do not receive texts from users on iD or Three. To the sender they look as though they have gone but I do not get them. Texts from other networks are received fine. Voice calls are fine. Live chat wouldn't raise an incident, the complaints procedure did but they just want to blame EE(Lyca). All the evidence points to a flawed port out and Three(iD) still trying to deliver the texts within their network so I am reluctant to blame EE(Lyca). I have been quoted the “ILLEGAL_SUBSCRIBER” message that they are getting but they would get that from their own network if they are trying to route internally as I’m not there anymore. I am still a customer on iD and Three and am using those numbers to raise an incident and for testing. Any advice would be appreciated.