MTN shocking network

I recently renewed my contract with mtn which gives me 250gb of data for R422…………80 gigs is data share which I share with 3 of my family members and the remainder data is promotional which I use in a router and my family connects to this. Now the issue is that the data on the data share is quite fast with no issues but the promotional data is so slow that it frustrates everyone in the house,even Facebook reels buffer that’s how slow the speed is. I called customer care many times and each time I get told to switch my router off and they are resetting my card which makes absolutely zero difference. The last time I called in I had the customer representative check my speed at my address and she tells me I have a 50mbps line available……I barely get a fraction of this speed,I even told her a snail that’s sick is faster then mtns speed. I regularly do speed tests on both cards(the data share and router) and I get 22-30 mbps on my data share cards and I run a speed test immediately after that on the router and my speeds are between 2-5mbps…I have screenshots and screen recordings of this to prove it! What makes it better is I check the speed from 5 in the morning(when not many people are using the network)right through the day and the speed is still shockingly slow.

Do I have a case to cancel and terminate this contract with the evidence I have as screenshots and screen recordings?

I’m really disgusted at mtn