Some drivers have reported circumstances when a pop-up appears on their mobile device and it asks for an iTunes account password. A reason the continuous pop-up of the iTunes account password keeps appearing is because it may be that your mobile device does not have the correct password saved on the device.
I own my mobile device. If you own your mobile device and you are uncertain to what your iTunes password is, you should connect with Apple to obtain instruction to getting your iTunes password.
My company provided me the mobile device I work from. If your mobile device was provided by your company, it may very well be the circumstance they had to establish an iTunes account in order to prepare the device for use. In the circumstance, you will need to get hold of your IT administrator within the Carrier company you work for.