Have you tried ringing your mobile phone from another phone? Are the calls not getting through at all, are they being forwarded to another number, or is it simply that your phone isn't ringing when you receive a call?
The following applies to the big X10. It will be a bit different on the mini or mini pro.
If it's just that the phone is not ringing, it might be that you've set it to silent. Press the menu button and select settings - sound and display. The first box in the menu is for 'Silent mode'. If there is a tick by that, tap it to remove the tick. Also look at Ringer volume, the next box in the list. There is a bar under incoming call volume. If the slider is to the left, there will be no incoming call volume; drag the slider to the right to resolve that. You can also adjust the volume of incoming calls by using the volume buttons on the right hand side when you're looking at the phone (with the display facing you!)
You don't give much infortmation in your message. If the above doesn't sort things out, post more details, including which of the X10 phones you have, and with any luck someone will be able to help you.
