Share your experience!
Why do you need to change it?
That's rather odd, what if you factory reset the phone?
even with XC?
Before trying XC, open the dialer and type *#*#4636#*#*
Tap phone information, then scroll down, check the screenshot attached, look where I typed HERE, that is the field where you have to put your SMSC number and then tap update.
Try to send an SMS and let me know if it worked. 