I have just had a long discussion with the EE help desk, at the end of which we established that from the My EE page left hand side, menu, switch accounts, allows you to select the account which you wish to examine. As I have one monthly contract and one PAYG (in the car, so I can't interrogate the account from there, it is important to be able to check status and usage. If when you try and add the other number to your account it tells you there is already and account associated with that number, the above is how you can access the info. If you have not added the number already, then you have to go through the manage number, add number route. Best of luck
