After buying a software, it was deleted. Then the phone was sent four text messages. What happened? What should I do?

This kind of software is definitely not regular software, Trojan virus software or rogue hacker software, otherwise it will not send messages when uninstalling. The mobile phone is probably infected with Trojan virus, so you can back up important information and restore factory settings to deal with this situation. If it can't be solved, you can only get root permission, download 360 mobile phone first aid kit and return to normal after killing.