they say that they can't accept my phone since I used a different apple i.d in the phone I used!

I bought my iphone6 on February. Last month when I was updating my phone through connecting itunes I lost my internet connections and later when i tried again it says update error and the phone never worked. So I sent my phone through a service provider to get it solved. They asked me to off my icloud in my mac book so I did.

And they asked my apple i.d and password do I gave. But they say that they can't accept my phone since I used a different apple i.d in the phone I used!!I,

and that is not possible because I use the same i.d in my imac,mac book pro and my new iphone6 which got stuck while updating. Please help.