DATA being depleted yet i am not using it

there is something not right with my data usage with Cell C, not surprising though!! I have disabled my cell c mobile data cos I do not trust this network; from 1 October 2019 and was using my Vodacom hotspot! how is it that my data is being depleted? I called cell c call centre and the agent states I have 2.5 GB of data! how is that possible when I receive constant sms stating my data is decreasing! and how can my data disappear when my mobile data is off?? the agent further stated that I was on the internet from certain dates. I was not! my mobile data was off and I was using a hotspot! do I get charged for using a hotspot off another cell provider? I was told I was on the internet etc I WAS NOT ON THE DAYS THE AGENT MENTIONED!!!! what is going on? I am taking this to the Ombudsman! tired of being ********** for *********** mobile service!!!!!!

I did switch it on yesterday, 19 October and of course, the data is finished! FRUSTRATING!!!!!!!!!!!!! now I am on a hotspot, what is cell c going to do now, charge me for using another networks hotspot!!!! I AM SO LIVID!!!