The first thing you need to fix is sending spam messages on behalf of a user to other contacts on his/her list. Here is a typical example that was automatically sent from my phone to a contact on my list without my consent:

"Happy Dussehra! Join hike this weekend & get a festive bonus of Rs. 51 free talktime on joining. It's 5 times faster with 10 new features. http://hike.in"

I'm thinking of reporting this to relevant authorities.