Hi @jin.irie. As per your given message;
"Hello @Felix. Thank you for the response. I am currently using my SIM, inserted to another phone and everything is working well. I just used one sim on my FLASH 2 before. I have the right settings for the SMS. I even checked the Message Centre No. a couple of times. Although it takes time sending sms, my main problem is receiving. I can't receive any sms if I won't send one. What I did before is I send one SMS to my own no. so that I could receive all the pending sms that were sent to me."
I already asked one of our team to look into this matter and escalate to our specialist team. While it's on process, I will also try get possible resolution. By the way, may I know what is the network provider you're subscribed with?