An icon will appear on the mobile phone. First it is a message, then it becomes an arrow. I can't get rid of it or send a message.

That arrow means that the mobile phone is sending information! Obviously, there is something wrong with texting on the mobile phone, which leads to the failure of texting. You can check whether there is any mail you sent in the Outbox (sending mail), and then delete it. It may also be a problem with information settings! See if the center number has changed, and if so, change it. If not, you can restart! If not, contact customer service and labor service!