You have to call the hotline number 211 to get this fixed.
Hi cai0824 ,
Regarding on that issue, it is I think a glitch on the system but will mention it to the council. I also have the same issue on my account on the website. I have 5GB but it only shows 4GB on my account. You can still check ur balance using the Self Service option *143#.
Will update u once I have the answer. Will raise this to the concerned party.