If youve changed your SIM card, theres a way to import your account information, groups and settings. Keep in mind that your old number will be deleted. Make sure that your new SIM is active and able to receive SMSes and calls.
Tap on Menu > Settings > Account > Change Number and enter the old phone number in the first box, followed by the new number in the second one.
Go to Settings > Account > Change Number, Enter your old phone number in the first box, and your new phone number in the second box.