Vodacom reaping customer off with their fixed high data rates

I am in vodacom 5GB day and 5GB night bundle for R150 per month. I have been using the services since early 2018 with no complaints. Last year December I started started experiencing an early depletion of my data both daytime and night time data. Same thing occurred January 2019. I have not changed my device or my device settings or the way I utilize the internet. Now February 2019 I have the same problem where my data does not last longer like it used to carry over every month. My data is depleted with 2 weeks in a month. Still using the same device and have not changed device settings.

All these things now that I think about it started when I refused to take another offer from vodacom of 20GB day time and 20GB night time data at R199, I refused this deal because already I have a deal with vodacom of which my upgrade is only due September this year.

I suspect vodacom having fixed data rates because really it's unfair of what they doing. I end up buying 1GB of data from MTN which pushes me to almost 3 weeks of internet connection.

Why is my data not lasting me the entire month since December, is this Vodacom's way of forcing us to take another contract with them if data? This is unfair. I had purchased a phone with vodacom a few days ago, it's on its way with the courier, I am going to return it once I receive it and go to another network that doesn't reap people off like I have experienced with vodacom. My wifi SIM card number (066) ********** Annoyed 11 years vodacom customer