Capped LTE

I have never experienced such bad service like I have with Supersonic. I signed up for a CAPPED LTE 120Gb package which now I'm told there was a system glitch which made me go over the initial plan. I was then told to top up which oli topped up 15gigs only to be told that I am on a minus that I need to top up more which is absurd. Why am I been charged for a system glitch which the advisor admitted to. What is the meaning of CAPPED if you allow clients to go over? I'm really not happy and when you call you get rooted from 1 person to the next no one wants to take ownership of this mess.