Same data package is R30 cheaper at MTN

I signed up for a data package - 2gb data with router for R120. This was approximately two months ago. Now I see MTN is running their special for 2gb data and router going for R89. So for a similar deal (if not the same deal), MTN is R30 cheaper? I suddenly feel like I am being overcharged. I am also due for an upgrade on my cellular contract this month and am considering shopping the deals with other service providers.