You should turn the matter over to your insurance company for coverage and defense. The insurance company should guide you as to the defense of the small claim action.
If you do not have insurance, then you can simply go in and tell the judge your side of the story. You could also hire an attorney to help you present your side of the story. If you do have insurance, then you should notify them immediately and they will need to provide you with a defense. Good luck!
You should file a counterclaim for your own damages, and ask the clerk about how to get a subpoena duces tecum for their cell phone records. You would certainly benefit from hiring a lawyer to assist you, but there are cost/benefit concerns, as you will need to pay the lawyer win or lose. Avoiding a $6000 judgment against you and recovering your own losses may be worth paying a lawyer, but as others have noted, how the accident occurred is important. Schedule a confidential consult with an attorney in the county where the case is venued.
This answer is provided for general information only. No legal advice can be given without a consult as to the specifics of the case.