Disappearing of data

My data disappeared and was advised via SMS that I would be reimbursed for the mistake. I checked my balance and had just over 800mgb on the 26th of Aug. I use wifi all day long at home. I called the call center this morning after I received an SMS that my data is again zero. The only explanation she gave me and expects me to just accept is that it shows her on the system that I connected to the internet. I find this ridiculous. It's not a lot of money but it's the principle. If i believed I used the data I wouldn't be esostinf my time holding on for ten min and arguing with an agent for a call that lasted almost 20min. They have no way of proving anything or give an explanation that makes sense and one must just walk away. This is daytime *******.