IPhone 5 dual SIM adapter problem?

The dual adapter works fine when I have a payg Orange and a payg T-Mobile SIM in place, but whenever I remove either SIM and insert my contract EE SIM, the phone displays 'invalid SIM'.

I'm obviously wanting to use my contract EE SIM in conjunction with any of the 2 payg SIMS.

Any ideas are greatly appreciated.

Thanks!

Steven

Added (1). I forgot to mention that the EE SIM works on my EE locked phone perfectly well.

Your EE SIM must be burned out. You need to exchange it with a new one.