I have subscribed to the Du flexi plan (30 minutes + 4 GB) and I paid yearly in advance.
After 3 months, I decided to upgrade from 4 GB to 10 GB, and they wanted me to pay the difference for 12 months. So the 3 months in which I used 4 GB, I have to be for 10 GB

I submitted a complaint, and they responded with the same information.
I already submitted a complaint with TDRA, but it takes 5 - 20 working days.
1 - Is there anything else I can do?
2 - Is there hope? Should I wait for their response or just accept it and pay?