Why can my Samsung A7 only receive text messages but not send text messages?

If your mobile phone cannot send text messages, it is recommended that you check whether you can make and receive calls. If not, please check whether the signal of the machine is stable and whether the phone bill is sufficient. If the phone can receive and receive calls normally but cannot send text messages, it is recommended that: 1. Check whether the information center number is correct (please contact the local network operator for the information center number. Telecom cards do not have information center number settings) 2. Try changing other SIM cards . 3. Check whether the machine has firmware/system update push notifications. If so, please upgrade the phone to the latest version. 4. If it doesn't work, please back up the data in your phone (contacts, multimedia files, etc.) and restore the machine to factory settings. If the problem still persists after the above operations, please bring your purchase invoice, repair card and machine to a Samsung service center for inspection.