"I am glad to inform you that our internal team granted our refund request for 6 months worth of Google Drive subscription. I tried to request for more than 6 months but this is the maximum that they can provide."
So last 5 years they charged me for Google Workspace which includes google drive and at the same time separately for google drive. Case closed, problem (for them) solved.
Really? What will you advice to do next ?
They've already refunded the time frame that might have been chargeback-able.
Even if you could chargeback further back than that, you risk retaliation to your Google accounts if you proceed with that.
The best thing for you in the long-run is to transition away from Google's services. Their lack of support for most people makes them too much of a risk to run your life with them.