If the handle has broken after a while, it may be worn and needs to be replaced.
You can buy new handles on swixsport.com and change as follows:
1. You heat up the old handle and pull it off.
2. Use glue on the end of the tube and heat it until it becomes liquid.
3. Put on the new handle. Make sure it is fully pulled down on the pole and the correct way.
If you think it's a warranty issue, contact the store where you bought the poles.