Slowly Swapping: Two Offers

The father and son were having a great time and had forgotten about their problems until Mikey's phone buzzed again. This time the message wasn't from Biff. Mikey checked the phone. It was from someone named Melissa. It said, "Sorry you are stuck at home...want company after school?" Well, it said that, but using a bunch of abbreviations. Whose phone was this? And why did people think it was his? Meanwhile, the former owner of the phone was...