Dear Deepak, I don't have any experience with that particular bacteria, however, for long time storage I recommend microbank (please see the attached link). I use it for long-term storage of bacteria and yeast and it works really well.

http://www.pro-lab.com/products-microbank.php?country=LV

you can use three different osmoprotectants like proline, glycerol, PEG and increase the stock medium to 30% (10% from each osmoprotectant with fresh sterilized suitable medium for Campylobacter )

Thank you everyone for the suggestions. I will definitely try skim milk buffer suggested by Stefan Zimmermann.

Thanks!

Deepak