D2

Positive: It's easier and faster sending a message rather then phoning them in, and it's safe so you know the person will receive your sent message, it also saves you time by quickly messaging them rather then phoning them and speaking them through, also it will cost you less by sending a message then speaking on the phone for a quite long time so each minute there money will be taken off they're credit.

Negative: If you don't have the persons phone number in you'r contacts or somewhere else in your phone you won't able to text that person as you don't have they're phone number, also sometimes the person might not receive the text because the message is too long or the person has sent lots of messages already so every message is taking its time to load and send, and  last is if the person is busy, they might not able to text you back and keep you waiting till they text back if it's really important. 

A second way of sending a message to the person is either by social network such as Facebook, almost everyone has Facebook now a days so you could just easily type in the persons name your looking for, find they're name and click to send a message to them and soon when they get online on Facebook they will receive the message eventually, this is also a good way of sending messages because it's free, quick and fast and you know the person will get you'r message.