I Cannot Send SMS from My Samsung SM B310E Despite Correct Settings

For the past two days, I have been unable to send SMS messages to any number from my Samsung SM-B310E keypad phone. My carrier is Türk Telekom, and I have checked the message center number, which is correct. I removed and reinserted the SIM card, but the issue persists. When I insert the same SIM card into another phone, I can send SMS without any problems, which means the issue is with the phone. Additionally, SMS-based transactions with Türk Telekom also cannot be completed. My boyfriend is in the military, so we are unable to communicate, which is causing significant hardship. I purchased the device with cash, and since I was told it is not under warranty, I cannot receive technical support. I also tried to contact customer service but was unsuccessful. I am requesting support to resolve this issue and restore the phone’s ability to send SMS.