I can't receive text message on iPhone?

I just used a "Gevey sim" to "unlock" my iPhone 4s from AU KDDI(Japan) and the unlocking went pretty well. However, my iMessage is still using my former japanese number even when i'm nolonger in Japan. I have read forums for advice on how to change the number but all the advice give nthere has failed to work for me. With Wi-Fi, i can still use iMessage though with my old number, and without Wi-Fi, i can only RECEIVE text message from friends but when i send, all texts are "failed".
Why is it that i'm able to receive the sms messages and yet i can't send? And how can i change to my new number without using the old number?
Please advise.

You will have to buy a new phone. Sorry, Charlie.

  • Will my message be delivered if sent as text message on iphone? My friend said that she was having phone problems earlier today. My message was being sent as an imessage, but I guess she wasn't receiving everyone of them, just getting the notifications that they were sent to her but she couldn't read them. I then responded to her, but it was sent as a text message this time and i have gotten no response. I'm not as much concerned about her responding or not, I just want to know if she will receive the message.
  • Why don't I receive alerts or a notification when I receive a text and I already checked my settings? I adjusted my setting and even put the ringer and notifications on and put the volume and ringer on and I receive no alert, no pop up, alert or notification when someone texts me. Why? This is the iPhone X! I went to the cell phone/ carrier store and they didn't help me. They said to go to the apple store or check the settings. I already adjusted the settings. So what do I do now?
  • Why can't I send/receive photos via text message on my iPhone? I have an iPhone 4S, which I bought unlocked and I use Straight Talk. I can't receive or send photos to contacts that don't have iPhones. Can anyone tell me why this is, and help me get it working?
  • What should you do when you receive a spam text message? Just received a text message from someone pretending to be DFS about an order I never ordered. The funny thing is when you go into the information on my iPhone; no phone number shows up. I contacted Three Mobile and they say they can't detect what activity goes on; on my phone. They recommended that I just ignore the sender. I've also blocked the sender; because the iPhone allows you to do that.