Sixt blocked my account
 

Anyone have this before? I had a rental right when Covid broke out and had to return my car a day later due to the airports practically shutting down. Long story short, they charged me for the full rental even though I was able to cancel. I disputed the charge with them and than my CC and my CC said I have to pay the balance, which I did. End of story, or so I thought.
I now try making a reservation and I see that my account is blocked from renting. Call customer service, email them and no response from anyone.
Any suggestions?

It is very common for certain businesses to stop doing business with those who initiate chargebacks which are not justified. Chargebacks are time-consuming and expensive to process and some companies simply do not view it as worthwhile.

You say that you have called. Have you not spoken with anyone?

I would simply ask what is wrong and not launch into a discussion of what you think may be the problem.

I have called customer service and they tell me it has to go through a special division and to email them. I did, a couple of times and no response.

Justified is relevant. I still feel that it was justified but according to the fine print of the contract the CC company wasn't able to side with me. Doesn't mean I'm wrong.

I called and emailed countless times and no response at all.

1. Stop calling and emailing. More than once is too often.
2. "Justified" is far from relative. Either a chargeback is supported or it is not. I don't know the facts of your contract and what you refer to as "fine print" but if you agreed to something and then dispute it through a chargeback, that is not a justified chargeback and it would not be odd for the merchant vendor to no longer do business with you.

Whether Sixt has fired you because of the chargeback incident or something else, the fact is that it apparently no longer wants you as a customer. I would move on and use another agency.

Exactly, there are other companies around and Sixt is sadly loosing frenchises...
This said, I would NEVER initiate a charge back with a company I am still interested in doing business with. It is a hostile act contrary to dialogue and may be justified, but only as a last resort.

You aren't alone. I disputed a charge and the credit card took my side. I am now banned for life from Sixt. Meh. I don't care.