Sorry, I don't understand this.Mobiles are not harmful because of their wrong use.
Because it would mean that mobiles are harmful (always), and that the reason for this is that they are (always) used wrongly.why not use "because of"?
If I use "sometimes", then I think it would be OK.Because it would mean that mobiles are harmful (always), and that the reason for this is that they are (always) used wrongly.
But that is not the case. They are not always harmful and are not always used wrongly. They are only harmful if and when they are used wrongly.
After all, this "wrong use" is wide-spread but does not always result in harm.