Unifi bill getting higher every month, Why is my Unifi bill getting higher?

Not sure if anyone else is experiencing this. I signed up with the VIP5 package, and I used to be billed around RM149.00 every month. Sometimes it fluctuates but it's usually around 149.

November 2012, my bill was RM149.05.
December 2012, it was RM149.10.
This month, it's RM150.90.

If anyone knows why, let me know? I would appreciate not having to call up customer service to ask.

Thanks!