mobile

Every type of sim works in my Samsung Galaxy S4 i9505 apart from EE sims. I have been back and forth with EE on the phone and to my local store and no-on knows what the issue is.

The phone is unlocked and was working fine with my (UK) T Mobile sim. Apparently the only difference between T Mobile and EE sims is the 4G part. Interestingly, a contract EE sim returns the message "Invalid Sim". A pay as you go EE sim returns the message "No Sim". My local EE store think this is a software issue rather than hardware.

Unlocked Samsung Galaxy S4
EE PAYG brings up "No Sim" error
EE contract sim brings up "Invalid Sim" error
All other networks' sims work fine
The IMEI is not blacklisted or blocked on EE
I have done a factory reset
AP: I9505XXUHOB7
CP: I9505XXUHOB7
CSC: I9505BTUHOB4

The problem is that I bought the phone off contract so EE cannot do anything and the warranty has expired. Has anyone ever heard of this problem before, and does anyone have any ideas as to what I could do next??