This is a natural process and should not be discouraged. Because while you would be having sex with your partner, you would be thinking of someone else, which is universally discouraged. Calling out the name of someone else in bed is embarrassing, to say the least. Because it reveals that you are thinking of someone other than your lover. And this is, albeit less egregious than the physical act, still cheating.
Sex is a state of mind as much as it is a state of body.
It requires an active participation of the consciousness of the people involved. Cheating must happen first mentally before it happens physically. This procession to physical from mental is all part of sex in any form - oral, intercourse, or cyber. Cheating begins in the mind. Cheating can be entirely performed in the mind, though to a slightly lesser degree.