NOKIA 2700 Classic automatic settings change

My sisters' NOKIA 2700 Classic phone setup email account sometimes request user name and password. when she setup email inbox in hear phone she gave correct username and password but after few weeks ago then again request username and password. sometimes show User name or password incorrect but hear Email account password and username didn't change. she gave same password for all seasons.
And also her phone profile automatic change (silent profile change General ) and date and time also automatic change.

why is that. Is it any virus effect.