Rising my installments and charging extra with no explanation!

I am confused why is cell c saying I owe them R286 for a contract that i have with them which initially started at R197pm and moved to R217pm. Now I see on my app that I owe R286. What is going on Cell C?

You guys trying to make extra money overnight? My account is up to date and now I see this? I want answers now else cancel my contract !