activation lock

i have an i phone 6s that developed a fault with a black screen following an update the phone was factory reset using i tunes using my apple i.d and password .the phone reset back to factory settings

when trying to set up the phone i got to select language and connecting to my internet,the phone then asked for for the activation lock to be removed using the same apple i.d and password that allowed me to reset it but it now says the i.d and password are incorrect i tried again now the phone is locked

how can apple allow me to reset the phone using their i.d and the state it is incorrect when setting up .....the phone is now a £700.00 paperweight and apple have been no help