Sentence 1: Will greatly missed his grandparents. 
 Sentence 3: His grandparents didn't own a cell phone at the time 
 Sentence 4:  One day, Will got a random call on his cell phone 
 Sentence 5:  He answered it and was surprised to hear from his grandparents 
 Option 1: His grandparents had moved to another state for warmer weather. 
 Option 2: His grandparents had passed away just over a month ago.